x+y=200 100x:{1.5*100y}=3:4 二元一次方程x+y=200 100x:{1.5*100y}=3:4 二元一次方程 怎么解? 速度...

二元一次方程帮忙解下(1)12.5x+13.3y-200=12x+13.5y12.9x+13.9y-1300=12.5x+13.3y x=?y=?(2)200x+150y=5500150x+100y=4000 x=?y=?(3)x+y=68100x+y-100y-x=2178 x=?y=? [3x^2-(x+y)(y-x)][2(-x-y)(y-x)+2x^2+3y^2],其中x=-2分之1,y=1.5 x+y=200和100x:1.5*100y=1:2怎么解.快 x>=1,x-y y=x-1(x 1 三元的 4x+8y+10z=100x+y+z=152 二元的 1.5x+2x=2101.5(x+y)=210 求导 y=[x/(1+x)]^x 1.5（x+y）+3（x-y）=27（x+y）-3（x-y）=-62.x-y/7 - x+y/10 =1/22(x-y)-5(x+y)=3所谓细节决定成败, y'-(1/x)y=xe^-x 10X+Y+1/3Z=10Y+X 10X+Y+2/3Z=100X+Y 14x+4y+z=200,x+y+z=100求解x,y,z 200(x-y)=400 100(x+y)=400,求X和Y x+y=100 2x=2/1y=92 X,Y得多少 z=0.015x*x+y*x*0.05+(1-x-y)*2.5*(x+y) x>0.35.xy>0.70x+y 已知|3x+y-0.5|+(x+2y+1.5)^2=0,求代数式（x-y)(x-2y)-3x(1/3x-y)+(2x+y)(2x-y) 快. 已知x+y=a,2x-y=-2a,求[（x/y-y/x)/(x+y)-x(1/x-1/y)]/[(x+1)/y]的值 x.y都是自然数,且x(x-u)-y(y-x)+12,求x.y得值快1且x(x-y)-y(y-x)=12 若2/x-1/y=3,求[y/x-y/x-y(x-y/x-x+y)]/x-2y/x的值