Question

In the arithmetic progression __ , 3, -1, -5, the missing term is .

• A. 7
• B. 1
• C. -7
• D. -1

Answer 1

Answer: (A), (D)

The correct options are
A 7
D -1

The $n^{th}$ term of an AP with the first term a and the common difference d is given by $a_n=a+(n-1)d$.

We know that, $a_2=3$ and $a_3=-1$
So, 3 = a + d ...(i)
and -1 = a + 2d ...(ii)

Subtracting equation (ii) from (i), we get,
4 = -d
d = -4

Hence, the missing term is
$a_1=a_2-d=3-d=3-(-4)=7$