Respuesta :

A(4,a)  B(a,11)

AB² = (a-4)² + (11-a)², EXPAND

AB² = a²-8a+16 + 121-22a+a²

AB² = 2a²-30a+137, but AB = 5 (given), therefore AB² =25
25 =  2a²-30a+137
OR 2a²-30a+112 = 0
It's a quadratic equation, Solve for a
a= 7 or a = 8