for an AP sum of first 10term is 4 times of first 5 term what is the commen difference and first term
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Given: S10 = 4 S5
We know Sn = n/2 [2a + (n-1)d], where a= first term of A.P. and d = common difference
10/2 [2a + (10-1)d] = 4 * 5/2 [2a + (5-1)d]
2a + 9d = 2 [2a + 4d]
2a + 9d = 4a + 8d
9d - 8d = 4a - 2a
d = 2a
a/d = 1/2
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Given: S10 = 4 S5
We know Sn = n/2 [2a + (n-1)d], where a= first term of A.P. and d = common difference
10/2 [2a + (10-1)d] = 4 * 5/2 [2a + (5-1)d]
2a + 9d = 2 [2a + 4d]
2a + 9d = 4a + 8d
9d - 8d = 4a - 2a
d = 2a
a/d = 1/2
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balakrishnan63:
what is the ratio of common diffrence and first term
in Answer .. in the 2nd stage were did 10/2 go???
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