Question

(x+1)^2-(2x-1)^2+3(x-2)(x+2) với x-1

Answer 1

(x+1)²-(2x-1)²+3(x-2)(x+2)

=x²+2x+1-4x²+4x-1+3(x²-4)

=x²+2x+1-4x²+4x-1+3x²-12

= 6x-12

= 6(x-2)

=6(-1-2)

=6.-3

=-18

Answer 2

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

\(=x^2+2x+1-4x^2+4x-1+3x^2-12\)

\(=6x-12\)(1)

Thay x=1 vào (1), ta được:

\(6\cdot1-12=6-12=-6\)