Answer :
x^2[tex](x+7)^2=x^2+10^2 x^2+14x+49=x^2+100 14x+49=100 14x=51 x=3.64[/tex]
It's a right triangle. So
(x²) + (10²) = (7+x)²
x² + 100 = 49 + x² + 14x
That may look ugly, but I'm pretty sure you can handle it from this point.
Wow ! I just noticed that you can subtract x² from each side
and not even have to mess with it again.