x^2y-2xy^2+y^3
=y(x^2-2xy+y^2)
=y(x-y)^2
(x+2y)^2-y^2
=(x+2y+y)(x+2y-y)
=(x+3y)(x+y)
x=y+7 ①
2x+y=3 ②
将①代入②中,得
2(y+7)+y=3
2y+14+y=3
3y=-11
y=-11/3
代入①中,得
y=10/3
3x-y=5 ①
4x-3y=5 ②
①×3,得
9x-3y=15 ③
③-②,得
5x=10
x=2
代入①中,得
y=1
x^a=3,x^b=5
x^(3a-2b)
=[x^(3a)]/[x^(2b)]
=(x^a)^3/(x^b)^2
=(3^3)/(5^2)
=27/25解方程组的第二题，写错了啦！对不起，看成竖行了x=y+7① 3x-y=5②将①代入②中，得3(y+7)-y=53y+21-y=52y=-16y=-8代入①中，得x=-1 2x+y=3①4x-3y=5②①×2，得4x+2y=6③③-②，得5y=1y=1/5代入①中，得x=7/5