Bài 22: Đại lượng tỉ lệ thuận
<span data-v-0db8fc00="">Hướng dẫn giải Bài 6.17 (Trang 14 SGK Toán 7, Bộ Kết nối tri thức, Tập 2)</span>
<p><strong>Bài 6.17 (Trang 14 SGK Toán lớp 7 - Bộ Kết nối tri thức với cuộc sống - Tập 2):</strong></p>
<p>Cho biết x, y là hai đại lượng tỉ lệ thuận. Thay mỗi dấu “?” trong bảng sau bằng số thích hợp.</p>
<table border="1" cellspacing="0" cellpadding="0">
<tbody>
<tr>
<td style="text-align: center;" valign="top" width="61">
<p>x</p>
</td>
<td style="text-align: center;" valign="top" width="61">
<p>2</p>
</td>
<td style="text-align: center;" valign="top" width="61">
<p>4</p>
</td>
<td style="text-align: center;" valign="top" width="61">
<p>5</p>
</td>
<td style="text-align: center;" valign="top" width="61">
<p>?</p>
</td>
<td style="text-align: center;" valign="top" width="61">
<p>?</p>
</td>
<td style="text-align: center;" valign="top" width="61">
<p>?</p>
</td>
</tr>
<tr>
<td style="text-align: center;" valign="top" width="61">
<p>y</p>
</td>
<td style="text-align: center;" valign="top" width="61">
<p>-6</p>
</td>
<td style="text-align: center;" valign="top" width="61">
<p>?</p>
</td>
<td style="text-align: center;" valign="top" width="61">
<p>?</p>
</td>
<td style="text-align: center;" valign="top" width="61">
<p>9</p>
</td>
<td style="text-align: center;" valign="top" width="61">
<p>18</p>
</td>
<td style="text-align: center;" valign="top" width="61">
<p>1,5</p>
</td>
</tr>
</tbody>
</table>
<p>Viết công thức mô tả mối quan hệ phụ thuộc giữa hai đại lượng x và y.</p>
<p><em><strong>Hướng dẫn giải:</strong></em></p>
<table border="1" cellspacing="0" cellpadding="0">
<tbody>
<tr>
<td style="text-align: center;" valign="top" width="61">
<p>x</p>
</td>
<td style="text-align: center;" valign="top" width="61">
<p>2</p>
</td>
<td style="text-align: center;" valign="top" width="61">
<p>4</p>
</td>
<td style="text-align: center;" valign="top" width="61">
<p>5</p>
</td>
<td style="text-align: center;" valign="top" width="61">
<p><strong><span id="MathJax-Element-2-Frame" class="mjx-chtml MathJax_CHTML" style="margin: 0px; padding: 1px 0px; display: inline-block; line-height: 0; text-indent: 0px; text-align: left; text-transform: none; font-style: normal; font-weight: normal; font-size: 16.94px; letter-spacing: normal; overflow-wrap: normal; word-spacing: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; position: relative;" tabindex="0" role="presentation" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mstyle displaystyle="true" scriptlevel="0"><mfrac><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><msub><mi>y</mi><mn>1</mn></msub></mrow></mrow><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><msub><mi>x</mi><mn>1</mn></msub></mrow></mrow></mfrac></mstyle><mo>=</mo><mstyle displaystyle="true" scriptlevel="0"><mfrac><mrow class="MJX-TeXAtom-ORD"><mo>&#x2212;</mo><mn>6</mn></mrow><mn>2</mn></mfrac></mstyle><mo>=</mo><mo>&#x2212;</mo><mn>3</mn></math>"><span id="MJXc-Node-60" class="mjx-math" aria-hidden="true"><span id="MJXc-Node-61" class="mjx-mrow"><span id="MJXc-Node-80" class="mjx-mstyle MJXc-space3"><span id="MJXc-Node-81" class="mjx-mrow"><span id="MJXc-Node-82" class="mjx-mfrac"><span class="mjx-box MJXc-stacked"><span class="mjx-numerator"><span id="MJXc-Node-83" class="mjx-texatom"><span id="MJXc-Node-84" class="mjx-mrow"><span id="MJXc-Node-85" class="mjx-mo"><span class="mjx-char MJXc-TeX-main-R">−</span></span></span></span></span></span></span></span></span></span></span></span>3</strong></p>
</td>
<td style="text-align: center;" valign="top" width="61">
<p><strong><span id="MathJax-Element-2-Frame" class="mjx-chtml MathJax_CHTML" style="margin: 0px; padding: 1px 0px; display: inline-block; line-height: 0; text-indent: 0px; text-align: left; text-transform: none; font-style: normal; font-weight: normal; font-size: 16.94px; letter-spacing: normal; overflow-wrap: normal; word-spacing: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; position: relative;" tabindex="0" role="presentation" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mstyle displaystyle="true" scriptlevel="0"><mfrac><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><msub><mi>y</mi><mn>1</mn></msub></mrow></mrow><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><msub><mi>x</mi><mn>1</mn></msub></mrow></mrow></mfrac></mstyle><mo>=</mo><mstyle displaystyle="true" scriptlevel="0"><mfrac><mrow class="MJX-TeXAtom-ORD"><mo>&#x2212;</mo><mn>6</mn></mrow><mn>2</mn></mfrac></mstyle><mo>=</mo><mo>&#x2212;</mo><mn>3</mn></math>"><span id="MJXc-Node-60" class="mjx-math" aria-hidden="true"><span id="MJXc-Node-61" class="mjx-mrow"><span id="MJXc-Node-80" class="mjx-mstyle MJXc-space3"><span id="MJXc-Node-81" class="mjx-mrow"><span id="MJXc-Node-82" class="mjx-mfrac"><span class="mjx-box MJXc-stacked"><span class="mjx-numerator"><span id="MJXc-Node-83" class="mjx-texatom"><span id="MJXc-Node-84" class="mjx-mrow"><span id="MJXc-Node-85" class="mjx-mo"><span class="mjx-char MJXc-TeX-main-R">−</span></span></span></span></span></span></span></span></span></span></span></span>6</strong></p>
</td>
<td style="text-align: center;" valign="top" width="61">
<p><strong><span id="MathJax-Element-2-Frame" class="mjx-chtml MathJax_CHTML" style="margin: 0px; padding: 1px 0px; display: inline-block; line-height: 0; text-indent: 0px; text-align: left; text-transform: none; font-style: normal; font-weight: normal; font-size: 16.94px; letter-spacing: normal; overflow-wrap: normal; word-spacing: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; position: relative;" tabindex="0" role="presentation" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mstyle displaystyle="true" scriptlevel="0"><mfrac><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><msub><mi>y</mi><mn>1</mn></msub></mrow></mrow><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><msub><mi>x</mi><mn>1</mn></msub></mrow></mrow></mfrac></mstyle><mo>=</mo><mstyle displaystyle="true" scriptlevel="0"><mfrac><mrow class="MJX-TeXAtom-ORD"><mo>&#x2212;</mo><mn>6</mn></mrow><mn>2</mn></mfrac></mstyle><mo>=</mo><mo>&#x2212;</mo><mn>3</mn></math>"><span id="MJXc-Node-60" class="mjx-math" aria-hidden="true"><span id="MJXc-Node-61" class="mjx-mrow"><span id="MJXc-Node-80" class="mjx-mstyle MJXc-space3"><span id="MJXc-Node-81" class="mjx-mrow"><span id="MJXc-Node-82" class="mjx-mfrac"><span class="mjx-box MJXc-stacked"><span class="mjx-numerator"><span id="MJXc-Node-83" class="mjx-texatom"><span id="MJXc-Node-84" class="mjx-mrow"><span id="MJXc-Node-85" class="mjx-mo"><span class="mjx-char MJXc-TeX-main-R">−</span></span></span></span></span></span></span></span></span></span></span></span>0,5</strong></p>
</td>
</tr>
<tr>
<td style="text-align: center;" valign="top" width="61">
<p>y</p>
</td>
<td style="text-align: center;" valign="top" width="61">
<p><span id="MathJax-Element-2-Frame" class="mjx-chtml MathJax_CHTML" style="margin: 0px; padding: 1px 0px; display: inline-block; line-height: 0; text-indent: 0px; text-align: left; text-transform: none; font-style: normal; font-weight: normal; font-size: 16.94px; letter-spacing: normal; overflow-wrap: normal; word-spacing: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; position: relative;" tabindex="0" role="presentation" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mstyle displaystyle="true" scriptlevel="0"><mfrac><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><msub><mi>y</mi><mn>1</mn></msub></mrow></mrow><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><msub><mi>x</mi><mn>1</mn></msub></mrow></mrow></mfrac></mstyle><mo>=</mo><mstyle displaystyle="true" scriptlevel="0"><mfrac><mrow class="MJX-TeXAtom-ORD"><mo>&#x2212;</mo><mn>6</mn></mrow><mn>2</mn></mfrac></mstyle><mo>=</mo><mo>&#x2212;</mo><mn>3</mn></math>"><span id="MJXc-Node-60" class="mjx-math" aria-hidden="true"><span id="MJXc-Node-61" class="mjx-mrow"><span id="MJXc-Node-80" class="mjx-mstyle MJXc-space3"><span id="MJXc-Node-81" class="mjx-mrow"><span id="MJXc-Node-82" class="mjx-mfrac"><span class="mjx-box MJXc-stacked"><span class="mjx-numerator"><span id="MJXc-Node-83" class="mjx-texatom"><span id="MJXc-Node-84" class="mjx-mrow"><span id="MJXc-Node-85" class="mjx-mo"><span class="mjx-char MJXc-TeX-main-R">−</span></span></span></span></span></span></span></span></span></span></span></span>6</p>
</td>
<td style="text-align: center;" valign="top" width="61">
<p><strong><span id="MathJax-Element-2-Frame" class="mjx-chtml MathJax_CHTML" style="margin: 0px; padding: 1px 0px; display: inline-block; line-height: 0; text-indent: 0px; text-align: left; text-transform: none; font-style: normal; font-weight: normal; font-size: 16.94px; letter-spacing: normal; overflow-wrap: normal; word-spacing: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; position: relative;" tabindex="0" role="presentation" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mstyle displaystyle="true" scriptlevel="0"><mfrac><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><msub><mi>y</mi><mn>1</mn></msub></mrow></mrow><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><msub><mi>x</mi><mn>1</mn></msub></mrow></mrow></mfrac></mstyle><mo>=</mo><mstyle displaystyle="true" scriptlevel="0"><mfrac><mrow class="MJX-TeXAtom-ORD"><mo>&#x2212;</mo><mn>6</mn></mrow><mn>2</mn></mfrac></mstyle><mo>=</mo><mo>&#x2212;</mo><mn>3</mn></math>"><span id="MJXc-Node-60" class="mjx-math" aria-hidden="true"><span id="MJXc-Node-61" class="mjx-mrow"><span id="MJXc-Node-80" class="mjx-mstyle MJXc-space3"><span id="MJXc-Node-81" class="mjx-mrow"><span id="MJXc-Node-82" class="mjx-mfrac"><span class="mjx-box MJXc-stacked"><span class="mjx-numerator"><span id="MJXc-Node-83" class="mjx-texatom"><span id="MJXc-Node-84" class="mjx-mrow"><span id="MJXc-Node-85" class="mjx-mo"><span class="mjx-char MJXc-TeX-main-R">−</span></span></span></span></span></span></span></span></span></span></span></span>12</strong></p>
</td>
<td style="text-align: center;" valign="top" width="61">
<p><strong><span id="MathJax-Element-2-Frame" class="mjx-chtml MathJax_CHTML" style="margin: 0px; padding: 1px 0px; display: inline-block; line-height: 0; text-indent: 0px; text-align: left; text-transform: none; font-style: normal; font-weight: normal; font-size: 16.94px; letter-spacing: normal; overflow-wrap: normal; word-spacing: normal; white-space: nowrap; float: none; direction: ltr; max-width: none; max-height: none; min-width: 0px; min-height: 0px; border: 0px; position: relative;" tabindex="0" role="presentation" data-mathml="<math xmlns="http://www.w3.org/1998/Math/MathML"><mstyle displaystyle="true" scriptlevel="0"><mfrac><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><msub><mi>y</mi><mn>1</mn></msub></mrow></mrow><mrow class="MJX-TeXAtom-ORD"><mrow class="MJX-TeXAtom-ORD"><msub><mi>x</mi><mn>1</mn></msub></mrow></mrow></mfrac></mstyle><mo>=</mo><mstyle displaystyle="true" scriptlevel="0"><mfrac><mrow class="MJX-TeXAtom-ORD"><mo>&#x2212;</mo><mn>6</mn></mrow><mn>2</mn></mfrac></mstyle><mo>=</mo><mo>&#x2212;</mo><mn>3</mn></math>"><span id="MJXc-Node-60" class="mjx-math" aria-hidden="true"><span id="MJXc-Node-61" class="mjx-mrow"><span id="MJXc-Node-80" class="mjx-mstyle MJXc-space3"><span id="MJXc-Node-81" class="mjx-mrow"><span id="MJXc-Node-82" class="mjx-mfrac"><span class="mjx-box MJXc-stacked"><span class="mjx-numerator"><span id="MJXc-Node-83" class="mjx-texatom"><span id="MJXc-Node-84" class="mjx-mrow"><span id="MJXc-Node-85" class="mjx-mo"><span class="mjx-char MJXc-TeX-main-R">−</span></span></span></span></span></span></span></span></span></span></span></span>15</strong></p>
</td>
<td style="text-align: center;" valign="top" width="61">
<p>9</p>
</td>
<td style="text-align: center;" valign="top" width="61">
<p>18</p>
</td>
<td style="text-align: center;" valign="top" width="61">
<p>1,5</p>
</td>
</tr>
</tbody>
</table>
<p>Vì x và y là hai đại lượng tỉ lệ thuận, có <math xmlns="http://www.w3.org/1998/Math/MathML"><mfrac><msub><mi>y</mi><mn>1</mn></msub><msub><mi>x</mi><mn>1</mn></msub></mfrac><mo> </mo><mo>=</mo><mo> </mo><mfrac><mrow><mo>-</mo><mn>6</mn></mrow><mn>2</mn></mfrac><mo> </mo><mo>=</mo><mo> </mo><mo>-</mo><mn>3</mn></math> nên ta có công thức y = -3.x</p>
Xem lời giải bài tập khác cùng bài
<span data-v-0db8fc00="">Hướng dẫn giải Bài 6.18 (Trang 14 SGK Toán 7, Bộ Kết nối tri thức, Tập 2)</span>
Xem lời giải
<span data-v-0db8fc00="">Hướng dẫn giải Bài 6.19 (Trang 14 SGK Toán 7, Bộ Kết nối tri thức, Tập 2)</span>
Xem lời giải
<span data-v-0db8fc00="">Hướng dẫn giải Bài 6.20 (Trang 14 SGK Toán 7, Bộ Kết nối tri thức, Tập 2)</span>
Xem lời giải
<span data-v-0db8fc00="">Hướng dẫn giải Bài 6.21 (Trang 14 SGK Toán 7, Bộ Kết nối tri thức, Tập 2)</span>
Xem lời giải