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

Làm tính chia

a. (left[ {5{{left( {a – b} ight)}^3} + 2{{left( {a – b} ight)}^2}} ight]:{left( {b – a} ight)^2})

b. (5{left( {x – 2y} ight)^3}:left( {5x – 10y} ight))

c. (left( {{x^3} + 8{y^3}} ight):left( {x + 2y} ight))

Giải:

a. (left[ {5{{left( {a – b} ight)}^3} + 2{{left( {a – b} ight)}^2}} ight]:{left( {b – a} ight)^2})

( = left[ {5{{left( {a – b} ight)}^3} + 2{{left( {a – b} ight)}^2}} ight]:{left( {a – b} ight)^2} = 5left( {a – b} ight) + 2)

b. (5{left( {x – 2y} ight)^3}:left( {5x – 10y} ight)) $ = 5{left( {x – 2y} ight)^3}:5left( {x – 2y} ight) = {left( {x – 2y} ight)^2})

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

( = left( {x + 2y} ight)left( {{x^2} – 2xy + 4{y^2}} ight):left( {x + 2y} ight) = {x^2} – 2xy + 4{y^2})