Question

rút gọn (a+2b-c)(a+2b+c)-(a²+4b²-c²)

Answer 1

Lời giải:

$(a+2b-c)(a+2b+c)-(a^2+4b^2-c^2)=(a+2b)^2-c^2-a^2-4b^2+c^2$

$=(a+2b)^2-a^2-4b^2$

$=a^2+4ab+4b^2-a^2-4b^2=4ab$

Answer 2

\(=\left[\left(a+2b\right)^2-c^2\right]-\left(a^2+4b^2-c^2\right)\)

\(=a^2+4ab+4b^2-c^2-a^2-4b^2+c^2\)

\(=4ab\)