30x=0.8y 40(x-1)=y+25
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30x=0.8y 40(x-1)=y+25
用加减消元法来解,
用加减消元法来解,
150x=4y
40x=y+65
150x=4y (1)
160x=4y+260 (2)
(2)-(1):10x=260
x=26,y=975
40x=y+65
150x=4y (1)
160x=4y+260 (2)
(2)-(1):10x=260
x=26,y=975
x,y属于R*,且x+y=1,求证:(1)(x+1/x)(y+1/y)≥25/4 (2)(x+1/x)^2+(y+1/y
解方程组 30x=4/5y 40(x-1)=y+25
先化简再求值(x-y)(x+y)-(x-2y) 的完全平方+x(3x-5y)-(x-y)(x-2y),其中x=1/2 y
x+y=450;40%x+30=60%y
已知实数x,y满足(x+y)^2=1,(x-y)^2=25,求x,y的值
已知实数x,y满足(x+y)平方=1,(x-y)平方=25,求x,y得值
y=[x-1],
(x+y)(x+2y)(x+3y)(x+4y)=-40
1.已知1/x+1/y=-1/x+y,则y/x+x/y=?
{3(x+y)+3(y+x)=1,3(x+y)+4(y-x)=-1
{4/(x+y)+6/(x-y)=3 {9/(x-y)-1/(x+y)=1
(3x-y)^2+(3x+y)(3x-y),x=1,y=-2