Hướng dẫn Giải Bài 3 (Trang 68, SGK Toán Giải Tích 12)

Hướng dẫn giải Bài 3 (Trang 68 SGK Toán Giải Tích 12)

Bài 3 (Trang 68 SGK Toán Giải Tích 12): Rút gọn biểu thức: a) <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>log</mi><mn>3</mn></msub><mfenced><mn>6</mn></mfenced><mo>.</mo><msub><mi>log</mi><mn>8</mn></msub><mfenced><mn>9</mn></mfenced><mo>.</mo><msub><mi>log</mi><mn>6</mn></msub><mfenced><mn>2</mn></mfenced></math>; b) <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>log</mi><mi>a</mi></msub><mfenced><msup><mi>b</mi><mn>2</mn></msup></mfenced><mo>+</mo><msub><mi>log</mi><msup><mi>a</mi><mn>2</mn></msup></msub><mfenced><msup><mi>b</mi><mn>4</mn></msup></mfenced></math>. Hướng dẫn giải: a) <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>log</mi><mn>3</mn></msub><mfenced><mn>6</mn></mfenced><mo>.</mo><msub><mi>log</mi><mn>8</mn></msub><mfenced><mn>9</mn></mfenced><mo>.</mo><msub><mi>log</mi><mn>6</mn></msub><mfenced><mn>2</mn></mfenced><mo>=</mo><msub><mi>log</mi><msup><mn>2</mn><mn>3</mn></msup></msub><mfenced><msup><mn>3</mn><mn>2</mn></msup></mfenced><mo>.</mo><msub><mi>log</mi><mn>3</mn></msub><mfenced><mn>6</mn></mfenced><mo>.</mo><msub><mi>log</mi><mn>6</mn></msub><mfenced><mn>2</mn></mfenced><mo> </mo><mo>=</mo><mfrac><mn>2</mn><mn>3</mn></mfrac><msub><mi>log</mi><mn>2</mn></msub><mfenced><mn>3</mn></mfenced><mo>.</mo><msub><mi>log</mi><mn>3</mn></msub><mfenced><mn>6</mn></mfenced><mo>.</mo><msub><mi>log</mi><mn>6</mn></msub><mfenced><mn>2</mn></mfenced><mo>=</mo><mfrac><mn>2</mn><mn>3</mn></mfrac><msub><mi>log</mi><mn>2</mn></msub><mfenced><mn>2</mn></mfenced><mo>=</mo><mfrac><mn>2</mn><mn>3</mn></mfrac></math> b) <math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mi>log</mi><mi>a</mi></msub><mfenced><msup><mi>b</mi><mn>2</mn></msup></mfenced><mo>+</mo><msub><mi>log</mi><msup><mi>a</mi><mn>2</mn></msup></msub><mfenced><msup><mi>b</mi><mn>4</mn></msup></mfenced><mo>=</mo><msub><mi>log</mi><mi>a</mi></msub><mfenced><msup><mi>b</mi><mn>2</mn></msup></mfenced><mo>+</mo><msub><mi>log</mi><mi>a</mi></msub><mfenced><msup><mi>b</mi><mn>2</mn></msup></mfenced><mo>=</mo><mn>2</mn><msub><mi>log</mi><mi>a</mi></msub><mfenced><msup><mi>b</mi><mn>2</mn></msup></mfenced><mo>=</mo><mn>4</mn><msub><mi>log</mi><mi>a</mi></msub><mfenced open="|" close="|"><mi>b</mi></mfenced></math>