聯立方程......

1.
sub x=y+3 into 3x+2y=14
3y+9+2y=14
5y=5
y=1
x=4
2.
sub.x=(7+3y)/2 into 4x+5y=3
14+6y+5y=3
11y=-11
y=-1
x=2
3.
sub.x=7-yinto 5x-2y=0
35-5y-2y=0
7y=35
y=5
x=2
4.
sub.x=(2-2y)/3 into4x-3y= -20
4/3(2-2y)-3y=-20
8/3-8/3y-3y=-20
17/3y=68/3
y=4
x=-2
5.
sub.b=4-2a into a-2b=7
a-8+4a=7
5a=15
a=3
b=-2