7x+4y=3640 3x+6y=1560 x=?y=?
{3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1
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
{4/(x+y)+6/(x-y)=3 {9/(x-y)-1/(x+y)=1
若(x-y)/(x+y)=3 则(x+2y)/(6x-7y)等于
【2(x-y)^3-8(x-y)^2(x+y)+6y(x-y)^2】/2(x-y)^2=
4x-(2x+y+16)/2=-6y 2x+3y=7-x-2y
{3(x+y)+3(y+x)=1,3(x+y)+4(y-x)=-1
6(x-y)-2(x+y)=14 3(x-y)+(x+y)=5
3(x+y)-4(x-y)=11,2(x-y)+5(x+y)=27
(5x+3y)(3y-5x)-(4x-y)(4y+x)=