求救 ! 兩題代入法數學 5 點

1 > x+3y-5=2x+y-5=0 ( 請使用代入消元法 )
can be:
x+3y-5=0 (1)and
2x+y-5=0 (2)
form (1)
x=5-3y -(3)

put into (2)
2x+y-5=0
2(5-3y)+y-5=0
10-6y+y-5=0
-5y=-5
y=1

put y=1 into (3)
x=5-3y=5-3=2//

So x=2 and y=1//

2 > 3x-4y-18=5x+2y-4=0
can be:
3x-4y-18=0 -(1) and
5x+2y-4=0 -(2)

(1)+2x(1)=
3x-4y-18+10x+4y-8=0
13x-26=0
x=2

put into (1)
3x-4y-18=0
3(2)-4y-18=
4y=-12
y=3//
So x=2 , y= 3//

1>

x+3y-5=0 ---1
2x+y-5=0 ---2

IN 1 > x= -3y+5 ---
2(-3y+5) + y -5 =0
-6y+10 + y-5 =0
-5y=-5
y=1

x = -3(1) + 5
x = 2

THUS , x=2 . y=1

2>

3x-4y-18=0 ---1
5x+2y-4=0 ---2

(1x5)
15x -20y -90=0 --- 3
( 2x3) :
15x + 6y -12 =0 ---4

(3 - 4)
-26y - 78 =0
y=-3
Put it in to (1)
3x-4(-3)-18=0
x=2
Thus x=2 , y=-3