Question

Bài 9.Rút gọn biểu thức
a)-5x²+3x.(x+2)
b)-2x.(1-x²)-2x³

c)4x.(x-1)-4(x²+2x-1)
d)6x³-2x²(-x²-3x)

e)3x(x-1)-(1+2x).5x

f)-5x²-(x-6).(-2x²)
Giúp mình với mn 

Answer 1

\(a\\ -5x^2+3x.\left(x+2\right)=-5x^2+3x^2+6x=-2x^2+6x\\ b\\ -2x.\left(1-x^2\right)-2x^3=-2x+2x^3-2x^3=-2x\\ c\\ 4x.\left(x-1\right)-4.\left(x^2+2x-1\right)\\ =4x^2-4x-4x^2-8x+4=-12x+4\)

Answer 2

\(d\\ 6x^3-2x^2.\left(-x^2-3x\right)=6x^3+2x^4+6x^3=2x^4+12x^3\\ e\\ 3x.\left(x-1\right)-\left(1+2x\right).5x\\ =3x^2-3x-5x-10x^2=-7x^2-8x\\ f\\ -5x^2-\left(x-6\right).\left(-2x^2\right)=-5x^2+2x^3-12x^2=2x^3-17x^2\)