已知x+y=5,x-y=1求xy与x^2+y^2-xy的值

2024-12-25 16:56:32
推荐回答(4个)
回答1:

x+y=5,
(x+y)^2=25,
x^2+y^2+2xy=25
x-y=1,
(x-y)^2=1,
x^2+y^2-2xy=1
xy=6
x^2+y^2=13

回答2:

知x+y=5,x-y=1
x²+y²+2xy = 25 ①
x²+y²-2xy = 1 ②
①- ② 4xy= 25-1 = 24
xy = 24 / 4 = 6

x^2+y^2-xy
=x²+y²+2xy -2xy
= 25 - 12
= 13

回答3:

解:解方程组x+y=5
x-y=1
得到 x=3
y=2
则xy=6
x^2+y^2-xy=9+4-6=7

回答4:

专家犯低级错误