F. 2 Method of Elimination

2011-03-08 6:48 am
Solve by method of elimination.

‎{(1/x)+(2/y)=(5/6)......(i)
‎{(2/x)-(3/y)=(2/3)......(ii)

Let a=(1/x), b=(1/y).

From (i), a+2b=(5/6)......(iii)
From (ii), 2a-3b=(2/3)......(iv)

......

Thanks.

回答 (1)

2011-03-08 8:48 am
✔ 最佳答案
(1/x) + (2/y) = (5/6) ...... (i)
‎(2/x) - (3/y) = (2/3) ...... (ii)

Let a = (1/x), b = (1/y).

From (i):
a + 2b = (5/6) ...... (iii)

From (ii):
2a - 3b = (2/3) ...... (iv)

(iii)*2:
2a + 4b = (5/3) ...... (v)

(v) - (vi)
7b = 1
b = 1/7
Then y = 7

Put b = (1/7) into (iii):
a + 2(1/7) = (5/6)
a = (35/42) - (12/42)
a = 23/42
Then x = 42/23

Ans: x = 42/23 and y = 7
參考: miraco


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