已知x+y=3 xy=2则x²-y²的值
来源:学生作业帮助网 编辑:作业帮 时间:2024/06/22 08:38:43
![已知x+y=3 xy=2则x²-y²的值](/uploads/image/z/10095198-6-8.jpg?t=%E5%B7%B2%E7%9F%A5x%2By%3D3+xy%3D2%E5%88%99x%26%23178%3B-y%26%23178%3B%E7%9A%84%E5%80%BC)
已知x+y=3 xy=2则x²-y²的值
已知x+y=3 xy=2则x²-y²的值
已知x+y=3 xy=2则x²-y²的值
x+y=3
(x+y)²=9
x²+2xy+y²=9
x²-2xy+y²=9-4xy
(x-y)²=9-8
x-y=±1
∴x²-y²=(x+y)(x-y)=3×(±1)=±3
∵x+y=3 ∴y=3-x ∵xy=2 ∴x(3-x)=2 解得:x1=1 x2=2 ∴:y1=2 y2=1 故x²-y²=1-4=-3/4-1=3
不确定0.0
(x-y)²=(x+y)²-4xy=1 x²-y²=(x+y)(x-y)=3或者-3