Find four numbers in AP whose sum is 20 and sum of whose square is 120.

Asked by prasadnidhi | 1st Nov, 2010, 12:00: AM

Expert Answer:

Dear Student
Let a-3d,a-d,a+d,a+3d be 4 noumbers in Ap
According to given condition
(a-3d)+(a-d)+(a+d)+(a+3d) =20
so 4a =20 or a =5
Again
(a-3d)2+(a-d)2+(a+d)2+(a+3d)2=120
2(a2+9d2)+2(a2+d2) =120
2a2+10d2=60 or a2+5d2=30
Using a = 5 we get
5d2=5 or d = +1 or -1
So AP is 2,4,6,8 or 8,6,4,2
Regrads
Team Topper

Answered by  | 1st Nov, 2010, 09:32: AM

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