Question

Rút gọn biểu thức:

a) (x+1)² + (x – 1)² – 2(1 + x)(1 - x)

b) 2x(2x – 1)² – 3x(x+3)(x – 3) – 4x(x+1)²

c) 3(x + 2)² – (3x + 1)(x + 5) + (x + 5)²

Answer 1

a: Ta có: \(\left(x+1\right)^2+\left(x-1\right)^2-2\left(1+x\right)\left(1-x\right)\)

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

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

\(=4x^2\)

c: Ta có: \(3\left(x+2\right)^2-\left(3x+1\right)\left(x+5\right)+\left(x+5\right)^2\)

\(=3x^2+12x+12-3x^2-16x-5+x^2+10x+25\)

\(=x^2+6x+32\)