Giải bài 6.32 trang 24 SGK Toán 8 tập 2 - Kết nối tri thức

Đề bài

Thực hiện phép tính:

\(\begin{array}{l}a)\frac{{4{\rm{x}} - 6}}{{5{{\rm{x}}^2} - x}}.\frac{{25{{\rm{x}}^2} - 10{\rm{x}} + 1}}{{27 - 8{{\rm{x}}^3}}}\\b)\frac{{2{\rm{x}} + 10}}{{{{\left( {x - 3} \right)}^2}}}:\frac{{{{\left( {x + 5} \right)}^3}}}{{{x^2} - 9}}\end{array}\)

Lời giải chi tiết

\(\begin{array}{l}a)\frac{{4{{x}} - 6}}{{5{{{x}}^2} - x}}.\frac{{25{{{x}}^2} - 10{{x}} + 1}}{{27 - 8{{{x}}^3}}}\\ = \frac{{ - 2\left( {3 - 2{{x}}} \right)}}{{x\left( {5{{x}} - 1} \right)}}.\frac{{{{\left( {5{{x}} - 1} \right)}^2}}}{{\left( {3 - 2{{x}}} \right)\left( {9 + 6{{x}} + 4{{{x}}^2}} \right)}}\\ = \frac{{ - 2\left( {5{{x}} - 1} \right)}}{{x\left( {9 + 6{{x}} + 4{{{x}}^2}} \right)}}\\b)\frac{{2{{x}} + 10}}{{{{\left( {x - 3} \right)}^2}}}:\frac{{{{\left( {x + 5} \right)}^3}}}{{{x^2} - 9}}\\ = \frac{{2{{x}} + 10}}{{{{\left( {x - 3} \right)}^2}}}.\frac{{{x^2} - 9}}{{{{\left( {x + 5} \right)}^3}}}\\ = \frac{{2\left( {x + 5} \right)\left( {x - 3} \right)\left( {x + 3} \right)}}{{{{\left( {x - 3} \right)}^2}{{\left( {x + 5} \right)}^3}}}\\ = \frac{{2\left( {x + 3} \right)}}{{\left( {x - 3} \right){{\left( {x + 5} \right)}^2}}}\end{array}\)