Question

Rút gọn

(a+c)(a-c)-(a-b-c)(a-b+c)+b(b-2a)

Answer 1

\(\left(a+c\right)\left(a-c\right)-\left(a-b-c\right)\left(a-b+c\right)+b\left(b-2a\right)\)

\(=a^2-c^2-\left(a-b\right)^2+c^2+b^2-2ab\)

\(=a^2-c^2-a^2+2ab-b^2+c^2+b^2-2ab\)

\(=0\)

Answer 2

\(=\left(a^2-c^2\right)-\left(\left(a-b\right)^2-c^2\right)+b^2-2ab\)

\(=a^2-c^2-\left(a-b\right)^2+c^2+b^2-2ab\)

\(=\left(a^2-2ab+b^2\right)-\left(a-b\right)^2\)

\(=\left(a-b\right)^2-\left(a-b\right)^2=0\)