If a completing the square equation equals something that is not zero what do i do

Triangle xyz has vertices x(1,3), y(0,0)

Extra points! find the missing dimension! need asap

Maci and i are making a small kite. two sides are 10". two sides are 5". the shorter diagonal is 6". round all your answers to the nearest tenth. 1. what is the distance from the peak of the kite to the intersection of the diagonals? 2. what is the distance from intersection of the diagonals to the top of the tail? 3. what is the length of the longer diagonal?