Subtract $a^2+b^2-2ab$ from $a^2+b^2+2ab$.

Given:

 $a^2+b^2-2ab$ and $a^2+b^2+2ab$.

To do:

We have to subtract $a^2+b^2-2ab$ from $a^2+b^2+2ab$.

Solution:

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

$=2ab+2ab$

$=4ab$.

Therefore, $a^2+b^2-2ab$ subtracted from $a^2+b^2+2ab$ is $4ab$.