Respuesta :

x²=a
x=⁺₋√a
we have two solutions: -√a and √a;
we can suggest this equation:
√a - (-√a)=30
√a+√a=30
2√a=30
√a=30/2
√a=15
(√a)²=(15)²
a=225

The solutions are -√225=-15 and √225=15.

Answer: a=225