Question

Chứng minh rằng: y.(x + y) + (x - y).(x + y) = x(x + y)

Answer 1

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

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

=x(x+y)

Answer 2

Ta có : VT = y. (x+y) + (x-y) . (x+y)

= \(xy + y^{2} + x^{2} + xy - xy - y^{2}\)

= \(xy + x^{2}\)

= x(y+x)

= VP