Question

已知x,y为有理数,且(x的2次方+y的2次方)(x的2次方+y的2次方-10)+25=0,求x的2次方+y的2次方的值

Answer 1

(x的2次方+y的2次方)(x的2次方+y的2次方-10)+25=0

( x²+y²)²-10(x²+y²)+25=0

(x²+y²-5)²=0

x²+y²=5