數學問題5

12 & 14 & 16

2006-11-15 21:46:34 補充：
(X-2) X (X 2) = 423X = 42X = 141) X - 2 = 122) X = 143) X 2 = 16

2006-11-15 21:52:08 補充：
(X - 2) ＋ X ＋ (X＋2) = 423X = 42X = 141) X － 2 = 122) X = 143) X ＋2= 16頭先唔知點解唔見晒D＋

設三個連續的偶數為 A, B, C,

因為是連續的偶數,所以,B=A+2, C=B+2 =(A+2)+2=A+4

A+B+C=42
A+(A+2)+(A+4)=42
A+A+2+A+4=42
3A+6=42
3A=42-6
3A=36
A=36/3
A=12

B=A+2=12+2=14

C=A+4=12+4=16

三個連續偶數分別為12,14,16.

let the 1st even figure = 2x

then 2x+(2x+2)+(2x+2+2) = 42

6x+6 = 42

X = 6

the 3 even figures are i) 2 * 6 = 12 (ans.)
ii) 12 + 2 = 14 (ans.)
iii) 14 + 2 = 16 (ans.)

設較大and連續偶較細的數係x,y

x+(x-2)+(y-4)=42

Let the smallest namber be A,
A+A+1+A+1+1=42
3A+3=42
3A=42-3
3A=39
A=13

So the three nambers are 13,14,15.

2006-11-15 21:48:48 補充：
Sor...Let the smallest namber be A,A+A+2+A+4=423A+6=423A=42-63A=36A=12