Maths的代數(中一)

1.
1/2m + 1=1/9 - 1/6

兩邊各項分別乘以 18m：

(1/2m) x 18m + 1 x 18m=(1/9) x 18m - (1/6) x 18m

9 + 18m = 2m - 3m

19m = -9

m = -9/19

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2.
3/4t = 4/3(t - 7)

交叉相乘：

3 x 3(t - 7) = 4 x 4t

9t - 63 = 16t

7t = -63

t = -9

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3.
b/3 - (5 - b) = 3

兩邊各項項分別乘以 3：

(b/3) x 3 - (5 - b) x 3 = 3 x 3

b - 15 + 3b = 9

4b = 24

b = 6

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4.
2y + 1/5 = 3 - y

兩邊各項分別乘以 5：

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

10y + 1 = 15 - 5y

15y = 14

y = 14/15

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5.
2s/3 - 1 = (s + 2)/5

兩邊各項分別乘以 15：

(2s/3) x 15 - 1 x 15 = [(s + 2)/5] x 15

10s - 15 = 3(s + 2)

10s - 15 = 3s + 6

7s = 21

s = 3
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