Question

2x(x+21)^2−x^2(x+21)=0
x1=
x2=
x3=

Answer 1

2x(x+21)²−x²(x+21)=0
2x(x+21)²−x²(x+21)=(x+21)(2x(x+21)-x²)=(x+21)(2x²+42x-x²)=(x+21)(x²+42x)=x(x+21)(x+42)
x(x+21)(x+42)=0
x₁=0
x₂=-21
x₃=-42