Question

[Quân]

Tính:

a,2x(x - 1) - 3(x² + 4x) + x(x + 2)

b,(2x - 3) (3x + 5) - (x - 1) (6x + 2) + 3 - 5x

c,(x - y)(x² + xy + y²) - (x + y)(x²- y²)

Answer 1

[Minh Phương]

\(a.2x\left(x-1\right)-3\left(x^2+4x\right)+x\left(x+2\right)\) 

\(=2x^2-2x-3x^2-12x+x^2+2x\) 

\(=-12x\) 

\(b.\left(2x-3\right)\left(3x+5\right)-\left(x-1\right)\left(6x+2\right)+3-5x\) 

\(=6x+10x-9x^2-15-6x^2-2x-6x-2+3-5x\) 

\(=-15x^2+3x-14\) 

\(c.\left(x-y\right)\left(x^2+xy+y^2\right)-\left(x+y\right)\left(x^2-y^2\right)\) 

\(=x^3-y^3-x^3+y^3+x^2y-y^3\)

\(=y^3+x^2y\)