(x+7.5)²(x-7.5)²=36,x等于?如题

(x+7.5)²(x-7.5)²=36,x等于?
如题

(x+7.5)²(x-7.5)²=36
[(x+7.5)(x-7.5)]²=36
(x²-7.5²)²=36=6²
x²-7.5²=6① 或者 x²-7.5²=-6②
①x²-7.5²=6
x²=7.5²+6=62.25
x=±√62.25=±√249/2
②
x²-7.5²=-6
x²=7.5²-6=50.25
x=±√50.25=±√201/2
x=±√249/2 或 x=±√201/2