0.8x-1.7y=-7 …① 5x-3y=2 …②
0.8x-1.7y=-7 …① 5x-3y=2 …②
数学题……555{(3x+y)(3x-y)-(x-5y)(5x-y)-(x-2y)²÷(-4x),x=-2.y
已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y)
已知x=2,y=3,求代数式(x-y)*(x-y)^3*(x-y)^5*……*(x-y)^11
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
3x+4y=6①,x+2y=4② 2x+5y=16①,8x-7y=10②
(x+2y)/2+(3x-y)/3=5 ① 0.2(x+2y)+0.8(3x-y)=4 ②
① X+Y=3 Y=2X-3 ② x+2y=9 y-3x=1 ③3/x+1=y 2(x+1)=6 ④ y-x=3 7x-
解方程组(x+y)(x-2y)=-5 (x-y)(x+2y)=7
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
若(x-y)/(x+y)=3 则(x+2y)/(6x-7y)等于