Question

Answer 1

Bài 1: 

a: Ta có: \(5x^2\left(-3x^2+2x-1\right)\)

\(=-5x^2\cdot3x^2+5x^2\cdot2x-5x^2\cdot1\)

\(=-15x^4+10x^3-5x^2\)

b: Ta có: \(\left(-3x^3\right)\cdot\left(2x^2-\dfrac{1}{3}xy+y^2\right)\)

\(=-3x^3\cdot2x^2+3x^3\cdot\dfrac{1}{3}xy-3x^3\cdot y^2\)

\(=-6x^5+x^4y-3x^3y^2\)

 

Answer 2

Bài 2: 

a: Ta có: \(A=\left(x^2-2\right)\left(x^2+x-1\right)-x\left(x^3+x^2-3x-2\right)\)

\(=x^4+x^3-3x^2-2x+2-x^4-x^3+3x^2+2x\)

=2

b: Ta có: \(B=2\left(x^2+2x\right)-x^2\left(x+2\right)+\left(x^3-4x+3\right)\)

\(=2x^2+4x-x^3-2x^2+x^3-4x+3\)

=3