Respuesta :

Diagonal of a rectangle:
D²=W²+L²        ( W-width, L-length)
The area :  W*L= 13 ⇒  L=[tex] \frac{13}{W} [/tex]
D=[tex] \sqrt{W^{2} + (\frac{13}{W})^{2} } = \sqrt{W^{2} + \frac{169}{W^{2} } }= \\ = \sqrt{ \frac{W^{4}+169 }{W^{2} } }= \frac{ \sqrt{W^{4} +169} }{W} [/tex]