a) (x+3)(x-2)=x²+3x-2x-6 =x²+x-6

b) (x+6)(2x+1)= 2x²+12x+x+6 = 2x²+13x+6

c) (x-5)(2-x) = -x²+2x+5x-10= -x²+7x-10

d) (-x+1)(x-2)= -x²+x+2x-2= -x²+3x-2

e) (-5x-3)(2-x) = 5x²-10x+3x-6= 5x²-7x-6

f) (x+1)(x-2) = x²-2x+x-2= x²-x-2

=y(x-5)+2(x-50)

=y(x-5)+2(x-5)-90

=(x-5)(y+2)-90

a. (2x+3y)²= (2x)²+2.2x.3y+(3y)²

=4x²+12xy+9y²

b. 2(\(\dfrac{1}{2}\)x²+y)(x²-2y)

=(x²+2y)(x²-2y)

=x⁴-4y²

c, (x+y+z)²= [(x+y)+z]²

=(x+y)²+2(x+y)z+z²

=x²+2xy+y²+2xz+2yz+z²

=x²+y²+z²+2xy+2yz+2xz

Cho x + y + z = 0; xyz ≠ 0 . Tính \(A=\dfrac{x^2}{yz}+\dfrac{y^2}{xz}+\dfrac{z^2}{xy}\)

Rút gọn A = ( x + y + z )³ - ( x + y - z )³ - ( x - y + z )³ - ( -x + y + z )³

Cho  a³ - 3ab² = 2 ;  b³ - 3a²b = -11.

Tính :  M = a² + b².

Tính giá trị biểu thức: 

C = 3(x³ - y³) - 3(x + y)² biết: x - y = 2.