Choose the correct answer from the given four options:
In an $ \mathrm{AP} $, if $ d=-4, n=7, a_{n}=4 $, then $ a $ is
(A) 6
(B) 7
(C) 20
(D) 28
Given:
In an A.P., $d = –4,\ n = 7,\ a_n=4$.
To do:
We have to find the value $a$.
Solution:
We know that,
$n^{th}$ term of A.P. $a_n=a+( n-1)d$
On substituting the values,
$\Rightarrow 4=a+( 7-1)( -4)$
$\Rightarrow 4=a-24$
$\Rightarrow a=24+4$
$\Rightarrow a=28$
Hence, $a=28$.
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