巧解方程(1) (x²-1)²-2x²-1=0 (2) (m²+n²)(m²+n²-2)-8=0求

题目

巧解方程(1) (x²-1)²-2x²-1=0 (2) (m²+n²)(m²+n²-2)-8=0求
m²+n²的值 (3) （x+1分之1）²-2（x+1分之1）-8=0 （4）已知x²+y²+4x-6y+13=0,求x+y的值

答案

(1) (x²-1)²-2x²-1=0(x²-1)²-2(x²-1)-3=0(x²-1-3)(x²+1)=0,x²-4=0或x²+1=0(无实数根)X=±2.(2) (m²+n²)(m²+n²-2)-8=0(m²+n²)...