Câu 47 trang 12 SBT Toán 8 tập 1: Làm tính chia...

Làm tính chia

a. $\left[ {5{{\left( {a - b} \right)}^3} + 2{{\left( {a - b} \right)}^2}} \right]:{\left( {b - a} \right)^2}$

b. $5{\left( {x - 2y} \right)^3}:\left( {5x - 10y} \right)$

c. $\left( {{x^3} + 8{y^3}} \right):\left( {x + 2y} \right)$

a. $\left[ {5{{\left( {a - b} \right)}^3} + 2{{\left( {a - b} \right)}^2}} \right]:{\left( {b - a} \right)^2}$

$= \left[ {5{{\left( {a - b} \right)}^3} + 2{{\left( {a - b} \right)}^2}} \right]:{\left( {a - b} \right)^2} = 5\left( {a - b} \right) + 2$

b. $5{\left( {x - 2y} \right)^3}:\left( {5x - 10y} \right))\ $ = 5{\left( {x - 2y} \right)^3}:5\left( {x - 2y} \right) = {\left( {x - 2y} \right)^2}$

c. $\left( {{x^3} + 8{y^3}} \right):\left( {x + 2y} \right))\ $ = \left[ {{x^3} + {{\left( {2y} \right)}^3}} \right]:\left( {x + 2y} \right)$

$= \left( {x + 2y} \right)\left( {{x^2} - 2xy + 4{y^2}} \right):\left( {x + 2y} \right) = {x^2} - 2xy + 4{y^2}$