Bài 1:
a.
$A(x)=-2x^2+3x-2x+1-5x+2x^2-x+1$
$=-5x+2$
b.
\(B(x)=-x^3+x^2+x+x^2-8x+x^3+2x-1\)
\(=(-x^3+x^3)+(x^2+x^2)+(x-8x+2x)-1\)
\(=2x^2-5x-1\)
Bài 2:
a.
\(=\frac{-1}{3}x.3x^2+\frac{1}{3}x.12x=-x^3+4x^2\)
b.
\(=-3x.(-x)+(-3x).2x^3=3x^2-6x^4\)
c.
\(=-2x^2+2x+2x^2+6x=8x\)
d.
\(=-5x^2+15x+x-5x^2=-10x^2+16x\)
e.
\(=\frac{1}{4}x.12x-\frac{1}{4}x.8-2x^2-6x-x^2+2x\)
\(=3x^2-2x-2x^2-6x-x^2+2x=-6x\)
Bài 2:
a: Ta có: \(-\dfrac{1}{3}x\left(3x^2-12x\right)\)
\(=\dfrac{-1}{3}x\cdot3x^2+\dfrac{1}{3}x\cdot12x\)
\(=-x^3+4x^2\)
b: Ta có: \(-3x\left(2x^3-x\right)\)
\(=-3x\cdot2x^3+3x\cdot x\)
\(=-6x^4+3x^2\)
c: Ta có: \(-2x\left(x-1\right)+2x\left(x+3\right)\)
\(=-2x^2+2x+2x^2+6x\)
=8x
d: Ta có: \(-5x\left(x-3\right)+x\left(1-5x\right)\)
\(=-5x^2+15x+x-5x^2\)
\(=-10x^2+16x\)
e: Ta có: \(\dfrac{1}{4}x\left(12x-8\right)-2x\left(x+3\right)+x\left(-x+2\right)\)
\(=3x^2-2x-2x^2-6x-x^2+2x\)
=-6x
Bài 1:
a: Ta có: \(A=-\left(2x^2-3x+2x-1\right)+\left(2x^2-5x-x+1\right)\)
\(=-2x^2+x+1+2x^2-6x+1\)
=-5x+2
b: Ta có: \(B=\left(3x^2-x^3+x-2x^2\right)-\left(-x^3-x^2+8x-2x+1\right)\)
\(=-x^3+x^2+x+x^3+x^2-6x-1\)
\(=2x^2-5x-1\)
