Arithmetic Sequence

In an arithmetic sequence, the sum of three consecutive terms is 30 andtheir product is 910. Find the possible values of these three terms.

Solution :
Let (a - d), a and (a + d) be the three terms.

(a - d) + a + (a - d) = 30 ...... [1]
(a - d) * a * (a + d) = 910 ...... [2]

From [1] :
3a = 30
a = 10

Put a = 10 into [2] :
(10 - d) * 10 * (10 + d) = 910
100 - d² = 91
d² = 9
d = 3 or d = -3

Hence, the three terms are 7, 10, 13.

2011-09-18 17:02:14 補充：
發問時點數已扣除，刪除答案只會損人不利己。