Question

1.rút gọn biểu thức

a)x(x-y)+y(x-y)

b)7x(4y-x)+4y(y-7x)-(\(4y^2-7x\))

Answer 1

Bài 1: Rút gọn biểu thức

a) Ta có: \(x\left(x-y\right)+y\left(x-y\right)\)

\(=\left(x-y\right)\left(x+y\right)\)

\(=x^2-y^2\)

b) Ta có: \(7x\left(4y-x\right)+4y\left(y-7x\right)-\left(4y^2-7x\right)\)

\(=28xy-7x^2+4y^2-28xy-4y^2+7x\)

\(=-7x^2+7x\)

Answer 2

a, Ta có : \(x\left(x-y\right)+y\left(x-y\right)\)

\(=\left(x+y\right)\left(x-y\right)=x^2-y^2\)

b, Ta có : \(7x\left(4y-x\right)+4y\left(y-7x\right)-\left(4y^2-7x\right)\)

\(=28xy-7x^2+4y^2-28xy-4y^2+7x\)

\(=7x-7x^2=7x\left(1-x\right)\)