The $4^{t h}$ term of an AP is $14$ and its $12^{t h}$ term is $70$ . What is its first term?

- 10

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Solution

The correct option is A $- 7$
As we know for an AP with first term $a$ and common difference $d$ , genral term is $a_{n} = a + (n - 1) d$
$∴ a + 3 d = 14$ and
$a + 11 d = 70$
On subtracting both the above equations, we get
$8 d = 56$
or $d = 7$
$∴ a = - 7$

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