Question

Find sum
9+7+5+3+............to 14 terms

Answer 1

Answer:-56

Step-by-step explanation:

Use Sn=n/2(2a+(n-1)d)

a=9

d=-2

Answer 2

Given :

Find sum

9+7+5+3+............to 14 terms

To find :

Sum up to 14 terms

Solution :

First term (a) = 9

common difference (d) = 5 - 7 = -2

number of terms (n) = 14

Putting the value of a , d and n in this formula

$\implies\sf S_n=\frac{n}{2}(2a+(n-1)\times{d}$

$\implies\sf S_{14}=\frac{14}{2}(2\times{9}+(14-1)\times{-2})$

$\implies\sf S_{14}=7(18-13\times{(-2))}$

$\implies\sf S_{14}=7(18-26)$

$\implies\sf S_{14}=7\times{(-8)}$

$\implies\sf S_{14}=-56$