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5道计算题,速求X-1/X=3,求X^2+1/X^2已知X-Y=9,XY=5,求X^2+Y^2X^2+4X+Y^2-2Y

来源:学生作业帮 编辑:作业帮 分类:数学作业 时间:2024/05/24 00:48:15
5道计算题,速求
X-1/X=3,求X^2+1/X^2
已知X-Y=9,XY=5,求X^2+Y^2
X^2+4X+Y^2-2Y+5=0,求X,Y
X^2-3X+1=0,求X^4+1/X^4
(3+1)*(3^2+1)*(3^4+1)..(3^1024+1)=?
X-1/X=3,求X^2+1/X^2
两边平方
X^2-2*X*1/X+1/X^2=3^2
X^2-2+1/X^2=9
X^2+1/X^2=11
已知X-Y=9,XY=5,求X^2+Y^2
两边平方
X^2-2XY+Y^2=9^2
X^2+Y^2=9^2+2XY=81+2*10=91
X^2+4X+Y^2-2Y+5=0,求X,Y
(X+2)^2+(Y-1)^2=0
所以(X+2)^2=0,(Y-1)^2=0
X+2=0,Y-1=0
X=-2,Y=1
X^2-3X+1=0,求X^4+1/X^4
把X=0代入1=0,不成立
所以X不等于0
两边除以X
X-3+1/X=0
X+1/X=3
两边平方
X^2+2+1/X^2=9
X^2+1/X^2=7
两边平方
X^4+2+1/X^4=49
X^4+1/X^4=47
(3+1)*(3^2+1)*(3^4+1)..(3^1024+1)
=[(3-1)(3+1)*(3^2+1)*(3^4+1)..(3^1024+1)
]/(3-1)
=(3^2-1)*(3^2+1)*(3^4+1)..(3^1024+1)/2
=(3^4-1)*(3^4+1)..(3^1024+1)/2
=……
=(3^1024-1)(3^1024+1)/2
=(3^2048-1)/2