Bài 2:
a) \(\left(x^3+5x^2-2x+1\right)\left(x-7\right)\\ =x^4+5x^3-2x^2+x-7x^3-35x^2+14x-7\\ =x^4-2x^3-37x^2+15x\)
b) \(\left(2x^2-3xy+y^2\right)\left(x+y\right)\\ =2x^3-3x^2y+3xy^2+2x^2y-3xy^2+y^3\\ =2x^3+y^3-x^2y\)
c) \(x\left(1-3x\right)\left(4-3x\right)=x\left(4-12x-3x+9x^2\right)=4x-15x^2+9x^3\)
d)\(\left(x-1\right)\left(x+2\right)\left(x-3\right)=\left(x^2+x-2\right)\left(x-3\right)\\ =x^3+x^2-2x-3x^2-3x+6\\ =x^3-2x^2-5x+6\)
Bài 2:
a: Ta có: \(\left(x^3+5x^2-2x+1\right)\left(x-7\right)\)
\(=x^4-7x^3+5x^3-35x^2-2x^2+14x+x-7\)
\(=x^4-2x^3-38x^2+15x-7\)
b: Ta có: \(\left(2x^2-3xy+y^2\right)\left(x+y\right)\)
\(=2x^3+2x^2y-3x^2y-3xy^2+xy^2+y^3\)
\(=2x^3-x^2y-2xy^2+y^3\)
giúp mik giải 2 bài này vs ạ
