用代入法{3x-2y=54x+3y=1{x+y=85x-2(x+y)=-1

Question

用代入法{3x-2y=5 4x+3y=1 {x+y=8 5x-2(x+y)=-1

Answer 1

3x-2y=5 ①
4x+3y=1 ②
由①得：x=(5+2y)/3 代入②,得：4(5+2y)/3+3y=1,20+8y+9y=3,17y=-17,y=-1.
把 y=-1 代入①,得：3x+2=5, 3x=3,x=1.
x=1.
y=-1.

x+y=8 ①
5x-2(x+y)=-1②
整理②,得：5x-2x-2y=-1,3x-2y=-1.
由①得：x=8-y,代入:3x-2y=-1,得：3(8-y)-2y=-1,24-3y-2y=-1,5y=25,y=5.
x=8-y=8-5=3.
x=3.
y=5.