Question

Answer 1

3:

a: \(x\left(x-2\right)=x\cdot x-2\cdot x=x^2-2x\)

b: \(3x^2\left(2x^3-5\right)=3x^2\cdot2x^3-3x^2\cdot5=6x^4-15x^2\)

Bài 4:

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

\(=x^2\cdot3x^3+x^2\cdot2x+x^2\cdot1-3x^3\cdot1-1\cdot3x-1\cdot1\)

\(=3x^5+2x^3+x^2-3x^3-3x-1\)

\(=3x^5-x^3+x^2-3x-1\)

b: \(\left(5x^2-2x\right)\left(x^2-x+1\right)\)

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

\(=5x^4-7x^3+7x^2-2x\)