【已知x分之y等于2】已知x分之一减去y分之一等于2,求x-xy-y分之3x+5xy-3y..._数学_永恒哥峩4
编辑: admin 2017-15-06
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4
1/x-1/y=2
同时乘以xy
y-x=2xy
x-y=-2xy
[3(x-y)+5xy]/[(x-y)-xy]
=(-6xy+5xy)/(-2xy-xy)
=(-xy)/(-3xy)
=1/3
互助这道作业题的同学还参与了下面的作业题
题1: 若x分之1减y分之1等于2,则y减xy减x分之3x加xy减3y的值等于多少[数学科目]
x分之1减y分之1等于2
(y-x)xy=2
y-x=2xy
y减xy减x分之3x加xy减3y
=[3(x-y)+xy]/(y-x-xy)
=(-6xy+xy)/(2xy-xy)
=-5xy/xy
=-5
题2: 已知x分之一减去y分之一等于2,求x-xy-y分之3x+5xy-3y的值[数学科目]
1/x-1/y=2
(y-x)/xy=2
y-x=2xy x-y=-2xy
代入:(3x+5xy-3y)/(x-xy-y)
=(-6xy+5xy)/(-2xy-xy)
=1/3
题3: 已知x分之一减y分之一等于2,求X+3XY-Y分之3x-xy-3y的值[数学科目]
由x分之一减y分之一等于2 化简得:X—Y=-2XY
X+3XY-Y分之3x-xy-3y=X+3XY-Y分之X+3XY-Y+2X-4XY-2Y=1+(X+3XY-Y)分之2X-4XY-2Y
用X-Y=-2XY代入上面的公式中,最后得出结果为:-7
题4: 已知x加y分之xy等于2,求负x加3xy减y分之3x减5xy加3y[数学科目]
已知 xy/(x+y) = 2,求:(3x-5xy+3y)/(-x+3xy-y)
xy/(x+y) = 2得:xy=2(x+y)
(3x-5xy+3y)/(-x+3xy-y)
=(3x-9xy+3y+4xy)/(-x+3xy-y)
= -3 + 4xy/(-x+3xy-y)
= -3 + 8(x+y)/(-x+6x+6y-y)
= -3 + 8(x+y)/5(x+y)
= -3 + 8/5
= -7/5
题5: 【如果1\x-1\y=2,那么3x+5xy-3y\x-xy-y等于多少这是初二的数学题分式那一张的,有知道的请帮帮我,】[数学科目]
1/x-1/y=2
(y-x)/xy=2
y-x=2xy
(3x+5xy-3y)/(x-xy-y)
=[5xy-3(y-x)]/[-xy-(y-x)]
=(5xy-6xy)/(-xy-2xy)
=-xy/-3xy
=1/3