～聯立方程４～

1)y = 2x - 3 (i)
4x + y = 9 (ii)

From(i), 4x=2y+6(iii)

Substitute (iii) into (i)

2y+6+y=9

3y+6=9

3y=3

y=1

Substitute y=1 into (i)

1=2x-3

2x=4

x=2
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2)x-2y=0(i)
3x-y=10(ii)

From(i),x=2y(iii)
From(ii),6x-20=2y(iv)

Substitute (iii) into (iv)

x=6x-20

6x-x=20

x=4

Substitute x=4 into (i)

4-2y=0

-2y=-4

y=2

2007-01-03 17:59:07 補充：
Vocabularies1)Substitute ... into ...=代 ... 入 ...2)From ... =從 ...

Ｑ１）　y = 2x - 3
　　　　4x + y = 9
將第一式代第二式
4x + 2x - 3 = 9
6x=12
x=2
y=2x-3=1

Ｑ２）　x - 2y = 0
　　　　3x - y = 10
由第一式
x=2y
將x=2y代第二式
3(2y)-y=10
5y=10
y=2
x=2y=4