Question

find a_(1) if d = 2.5, a_(15) = 33.5, S_(15 )= 240

Answer 1

Answer:

Value of d is 20.

I hope it will help you.

Step-by-step explanation:

Answer 2

Answer:

$a_{1}=-19$

Step-by-step explanation:

It is sum of arithmetic progression again.

$S_{15}=\frac{15}{2} [2a_{1}+(15-1)\cdot 2.5]$

$240=\frac{15}{2} [2a_{1}+35]$

$240=15a_{1}+535$

$-285=15a_{1}$

$a_{1}=-19$