Question

已知X+Y的负一次方=10,X-Y的负一次方=6,求X的平方+Y的平方的值

Answer 1

1/(x+y)=10

x+y=1/10

(x+y)²=1/100

x²+y²+2xy=1/100①

1/(x-y)=6

x-y=1/6

(x-y)²=1/36

x²+y²-2xy=1/36②

①+②

2(x²+y²)=17/450

x²+y²=17/900