(x+1)(x-1)(x+2)(x-2)
= (x2 - 1)(x2 -4)
= x4 - 4x2 - x2 + 4
= x4 - 5x2 + 4
Ta có: \(\left(x+1\right)\left(x-1\right)\left(x+2\right)\left(x-2\right)\)
= \(\left(x^2-1\right)\left(x^2-4\right)\)
= \(x^4-4x^2-x^2+4\)
= \(x^4-5x^2+4\)
Vậy \(\left(x+1\right)\left(x-1\right)\left(x+2\right)\left(x-2\right)=x^4-5x^2+4\)
~ Chúc bạn học tốt ~
\(\left(x+1\right)\left(x-1\right)\left(x+2\right)\left(x-2\right)\\ =\left(x^2-1\right)\left(x^2-4\right)\\ =x^4-5x^2+4\)
\(\left(x+1\right)\left(x-1\right)\left(x+2\right)\left(x-2\right)\)
\(=\left(x^2-1\right)\left(x^2-4\right)\)
\(=x^4-4x^2-x^2+4=x^4-5x^2+4\)