～聯立方程３～

1)y - x = 2(i)
3x + 4y = 15(ii)

From (i),3y-6=3x(iii)

Substitute (iii) into (ii)

3y-6+4y=15
7y-6=15
7y=15+6
7y=21
y=21/7
y=3

Substitute y=3 into (i)

3-x=2
x=3-2
x=1
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2)b - 3a = 2(i)
5a + 2b = 15(ii)

From(ii),2b=4+6a(iii)

Substitute (iii) into (ii)

5a+4+6a=15
11a+4=15
11a=15-4
11a=11
a=11/11
a=1

Substitute a=1 into (i)

b-3 x 1=2
b-3=2
b=2+3
b=5
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Vocabularies
1)Substitute ... into ...=代 ... 入 ...
2)From ... =從 ...

Q1
y=2+x=(15-3x)/4,
x=1 and y=3

Q2
b=2+3a=(15-5a)/2,
a=1 and b=5

1.
y = x + 2

3x + 4y = 15
3x + 4(x + 2) = 15
7x + 8 = 15
7x = 7
x = 1
y = 3


2.
b - 3a = 2
b = 2 + 3a

5a + 2b = 15
5a + 2(2 + 3a) = 15
5a + 4 + 6a = 15
11a = 11
a = 1
b = 5