Question

Rút gọn biểu thức.

a)M=(x+3y)²-(x-3y)²

b)Q=(x-y)²-4(x-y)(x+2y)+4(x+2y)²

Answer 1

a) M = (x + 3y)² - (x - 3y)²

= [(x + 3y) - (x - 3y)][(x + 3y) + (x - 3y)]

= (x + 3y - x + 3y)(x + 3y + x - 3y)

= 6y.2x

= 12xy

b) Q = (x - y)² - 4(x - y)(x + 2y) + 4(x + 2y)²

= [(x - y) - 2(x + 2y)]²

= (x - y - 2x - 4y)²

= (-x - 5y)²

Answer 2

a)M=x^2+6xy+y^2-x^2-6xy+y^2

=2y^2