Question

PLEASE HELP

Answer 1

Look at the picture.

Use the Pythagorean Teorem:
$l^2+(5l)^2=d^2\\l^2+5^2l^2=d^2\\d^2=l^2+25l^2\\d^2=26l^2\\d=\sqrt{26}^2\\d=\sqrt{26}\cdot\sqrt{l^2}\\\boxed{d=l\sqrt{26}}$