中2數學．幫下我

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你都冇答過, 問咩對不對

1. a-b=a+2b-3=0
a-b=0...................(1)
a+2b-3=0.............(2)
From (1),
a=b..............(3)
Sub (3) into (2)
b+2b-3=0
3b=3
b=1
Sub b=1 into (3)
a=b=1

2. ｛x+2y=14........................(1)
{3x-2y=2.........................(2)
(1)+(2):
4x=16
x=4
Sub x=4 into (2)
3(4)-2y=2
y=5　

3 {4m-n=3..............................(1)
{3m+2n=16.........................(2)
(1)x2:
8m-2n=6..........(3)
(2)+(3):
11m=22
m=2
Sub m=2 into (1)
4(2)-n=3
n=5

4 {m-n=1..............................(1)
{2m-3n+2=0......................(2)
From (1),
m=n+1..........(3)
Sub (3) into (2),
2(n+1)-3n+2=0
2n+2-3n+2=0
-n=-4
n=4
Sub n=4 into (3)
m=4+1=5

1. a-b=a+2b-3=0
不對
a=1
b=1

2.｛x+2y=14
{3x-2y=2
　對

3.{4m-n=3
{3m+2n=16
對

4.{m-n=1
{2m-3n+2=0
對