Question

[Lan Đậu]

rút gọn biểu thức

a) (x-1)³ -(x-1)(x²+x+1)

b) (x-3)³ -(x-3)(x²+3x+9)+6(x+1)²

Answer 1

[Nào Ai Biết]

a)

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