Here's my problem: "In a rectangle, the diagonal is 6 and area 14. The perimeter is: a) 10 b) 14 c) 16 d) 18 e) 20.
So I know that $x^2 + y^2 = 36$, and that $xy = 14$, but I'm having problems figuring out what the width and height equals.. (sorry if anything's unclear, English is not my primary language , but I can't find any information on this in my own language).
Hint: try to use $(x+y)^2=x^2+y^2+2xy$