Question

已知（a方+b方-2）(a方+b方）=8,求a方+b方的值

Answer 1

(a^2+b^2-2)(a^2+b^2)=8

设a^2+b^2=t

(t-2)t=8

t^2-2t-8=0

(t-4)(t+2)=0

t=4

所以a^2+b^2=4