Find the sum :

9 + 7 + 5 + 3 +……to 14 terms.

The above sequence is an A.P. with common difference = 5 - 7 = -2.

We know that,

Sum of n terms of an A.P. is given by,

∴ S_n = $\dfrac{n}{2}$ [2a + (n - 1)d]

⇒ S₁₄ = $\dfrac{14}{2}$ [2(9) + (14 - 1)(-2)]

= 7[18 + (13)(-2)]

= 7[18 - 26]

= 7.(-8)

= -56.

Hence, S₁₄ = -56.