Question

What must be subtract from $a^2+b^2+2ab$ to get $-4ab+2b^2?$

Answer 1

Step: Subtracting $(-4ab+2b^2)$ from $(a^2+b^2+2ab)$
The answer can the found by subtracting $(-4ab+2b^2)$ from $(a^2+b^2+2ab).$
$=(a^2+b^2+2ab)-(-4ab+2b^2)$
$=a^2+b^2+2ab+4ab-2b^2$
$=a^2+b^2-2b^2+2ab+4ab$
$=a^2-b^2+6ab$
Hence, $(a^2-b^2+6ab)$ should be subtracted from $(a^2+b^2+2ab)$ to get $(-4ab+2b^2).$