if an ap 4 times of the 4 th term is equal to the 5 times of 5th term then which term is equal to zero
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4 (a+3d) = 5(a+4d)
4a+12d = 5a+20 d
a = -8 d
an = a+(n-1)d
For this to be zero , (n-1)d = -a
(n-1) d = - (-8d) ((which we derived previously)
(n-1) d = 8d
n- 1 = 8
n = 9
Therefore, 9th term is zero
4a+12d = 5a+20 d
a = -8 d
an = a+(n-1)d
For this to be zero , (n-1)d = -a
(n-1) d = - (-8d) ((which we derived previously)
(n-1) d = 8d
n- 1 = 8
n = 9
Therefore, 9th term is zero
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