x+y=8 (x+y)2 =x2+2xy+y2(x-y)的平方=4 (x-y)2=x2-2xy+y2则有x2+y2 =(x+y)2 +(x-y)2 /2=64+4 /2=34
x+y=8（x+y）^2=8^2=64x^2+2xy+y^2=64----(1)(x-y)^2=4x^2-2xy+y^2=4-----(2)(1)+(2)2(x^2+y^2)=68x^2+y^2=34
破问题有歧义
34
