计算下列各题,(5x+y)(3x-5x)-(4x-y)(4y+x)已知(x-y)^2=625/36,x+y=7/6,求x
来源:学生作业帮 编辑:作业帮 分类:数学作业 时间:2024/06/28 08:49:48
计算下列各题,
(5x+y)(3x-5x)-(4x-y)(4y+x)
已知(x-y)^2=625/36,x+y=7/6,求xy的值
解方程:(3x+2)(x-1)=3(x-1)(x+1)
(5x+y)(3x-5x)-(4x-y)(4y+x)
已知(x-y)^2=625/36,x+y=7/6,求xy的值
解方程:(3x+2)(x-1)=3(x-1)(x+1)
1.(5x+y)(3x-5y)-(4x-y)(4y+x)=15x²-25xy+3xy-5y²-(16xy+4x²-4y²-xy)
=15x²-22xy-5y²-15xy-4x²+4y²=11x²-37xy-y²
2.∵x+y=7/6
∴x²+2xy+y²=49/36①
∵(x-y)²=625/36
∴x²-2xy+y²=625/36②
①-②得4xy=-576/36=-16
∴xy=-4
3.(3x+2)(x-1)=3(x-1)(x+1)
3x²-3x+2x-2=3(x²-1)
3x²-x-2=3x²-3
-x=-1
∴x=1
=15x²-22xy-5y²-15xy-4x²+4y²=11x²-37xy-y²
2.∵x+y=7/6
∴x²+2xy+y²=49/36①
∵(x-y)²=625/36
∴x²-2xy+y²=625/36②
①-②得4xy=-576/36=-16
∴xy=-4
3.(3x+2)(x-1)=3(x-1)(x+1)
3x²-3x+2x-2=3(x²-1)
3x²-x-2=3x²-3
-x=-1
∴x=1
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