(x²+y²)(x² +y²+1)=20,求x²+y²急...

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(x²+y²)(x² +y²+1)=20,求x²+y²
急...

(x²+y²)(x² +y²+1)=20
=》(x²+y²)² + (x²+y²) = 20
=》(x²+y²)² + (x²+y²)+ 1/4 = 20 +1/4
=》(x²+y²+1/2)² = 81/4
=》 x²+y²+1/2 = 9/2
=》 x²+y² = 4