If the 9th term of an A.P is five times the 5th term, find the relationship between a and d.
The correct answer is C. a + 3d = 0
Let's denote the first term of the arithmetic progression as \(a\) and the common difference as \(d\).
The \(n\)th term of an arithmetic progression is given by the formula:
T_n = a + (n - 1)d.\)
Given that the 9th term is five times the 5th term, we can write the relationship as:
T_9 = 5T_5.\)
Substituting the formulas for \(T_9\) and \(T_5\), we get:
a + 8d = 5(a + 4d).\)
Now, simplify the equation:
a + 8d = 5a + 20d.\)
Subtracting \(a\) from both sides:
8d = 4a + 20d.\)
Subtracting \(20d\) from both sides:
-12d = 4a.\)
Dividing both sides by \(4\):
3a + 5d = 0.\)
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