Question

look at the picture attached for question

Answer 1

$SOLUTION:$

x²+y²+2xy-100

= (x+y)²-100

$( perfect square formula (a+b)² = a²+b²+2ab square variance formula a²-b² = (a+b)(a-b) )$

= (x+y)²-10²

So the answer Is

$=(x+y+10)(x+y-10)$