Giúp e vs ạ Cảm ơn mng nhiều

Câu 1

a,3x².(6x²-2x+1)

=18x^4 -6x^3 +3x²

b,(10x^4y-4x^2y^2+5x²y):2x²y

=2x²y(5x²-2y+$\frac{5}{2}$ ) : 2x²y

=(5x²-2y+$\frac{5}{2}$ )

Câu 2

a,4x²-8x=4x(x-2)

b,4x²-9y²+4x-6y

=(2x-3y)(2x+3y) + 2(2x-3y)

=(2x-3y)(2x+3y+2)

c,x²-2xy-16+y²

=x²-2xy+y²-(4)²

=(x-y)²-(4)²

=(x-y+4)(x-y-4)

Câu 3: 2(x+2021)-x²-2021x=0

<=>2(x+2021)-(x²+2021x)=0

<=>2(x+2021)-x(x+2021)=0

<=>(x+2021)(2-x)=0

=>$\left \{ {{x+2021=0} \atop {2-x=0}} \right.$ 

=>$\left \{ {{x=-2021} \atop {x=2}} \right.$