3x+6y=78 3x+4y=72 怎么解

推倒公式:(x+y)(x*x-3x+y*y)=x*x*x+y*y*y怎么做. 3x+6y=78 3x+4y=72 怎么解 二元一次方程(x+y)/2+(x-y)/3=6,4(x+y)-5(x-y)=2怎么算 3x+2=y 5x+4=y 7x+6=y 9x+8=y 11x=y怎么解 x+y/2+x-y/3=6,4(x+y)-3(x-y)=-20 {(x+y)/2+(x-y)/3=6 4(x+y)-3(x-y)=-20 4(x+y)-3(x-y)=-20,2/x+y+3/x-y=6 {3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1 （x+y）/2- x-y/2=6 3(x+y)=4(x-y) x+y/3+x-y/2=6 4(x+y)-2(x-y)=40 x^2-4xy+3y^2=（x-3y)(x-y)x^2-4xy+3y^2 怎么分解成（x-3y)(x-y) (x-y) (x-2y)+(x+2y) (x-3y)-2(x-3y) (x-4y)= 5x+4y=22 4x+y=3y+x 怎么解 请问算到4x/y=3y/x后怎么算出x,y, 【2(x-y)^3-8(x-y)^2(x+y)+6y(x-y)^2】/2(x-y)^2= 方程2x+y=3,4x-y=-1,6x+y+z=8怎么解 3x*5y+2x*6y=2.7*(3x+2x)怎么解 若(-x+6):(x-y):(4x+y)=3:14:1,求x+y