若a^2-1/a^2=3,求a^2+1/a^2

(a^2-1/a^2)^2=9
a^4+1/a^4-2a^2*1/a^2=9
a^4+1/a^4=11
a^4+1/a^4+2a^2*1/a^2=13
(a^2+1/a^2)^2=13
a^2+1/a^2=正负根号13>0
所以
a^2+1/a^2=根号13

a^2-1/a^2=3
所以a^4-2+1/a^4=9
a^4+1/a^4=11
(a^2+1/a^2)^2=a^4+1/a^4+2=13
因为a^2+1/a^2>0
所以a^2+1/a^2=根号13

(a-1/a)^2=a^2+1/a^2-2
(a+1/a)^2=a^2+1/a^2+2
上两式相乘
(a^2-1/a^2)^2=x^2-4
x^2=3^2+4
x=13^(1/2)

我不是他舅正确