幫幫手 一題既數學題目

3-2y 5 y-3 1
------ + ------ = ---------- + ----
4 12 2 3
通分母
3(3-2y) + 5 = 6(y-3) + 4
----------------------- ---------------------
12 12

(9-6y) + 5 = (6y-18) + 4

9-6y+5 = 6y-18+4

9+5+18-4 = 6y+6y

28 = 12y

28
---- = y
12

7
--- = y
3


答案:
y = 3分7

2007-01-22 22:00:03 補充：
帶分數 = 2又3分1小數 = 約2.33 (2.3333333333333333...........)

3 5 y 1
---- - 2y + ---- = ---- - 3 - ----
4 12 2 3

3 5 1 y
---- + ---- + 3 + ---- = ---- + 2y
4 12 3 2

9 5 36 4 5y
---- + ---- + ----- + ----- = -----
12 12 12 12 2

54 5y
---- = -----
12 2

108 = 60y

108 9 4
y = ------ = ----- = 1 ----
60 5 5

y = 一又五份四

2007-01-23 14:27:17 補充：
(3/4) - 2y (5/12) = (y/2) - 3 - (1/3)(3/4) (5/12) 3 (1/3) = (y/2) 2y(9/12) (5/12) (36/12) (1/3) = (1/2)y (4/2)y(54/12) = (5/2)y108 = 60yy = (108/60)y = (9/5) = 一又五分四