Answer:
Value of d is 20.
I hope it will help you.
Step-by-step explanation:
Answer:
[tex]a_{1}=-19[/tex]
Step-by-step explanation:
It is sum of arithmetic progression again.
[tex]$S_{15}=\frac{15}{2} [2a_{1}+(15-1)\cdot 2.5]$[/tex]
[tex]$240=\frac{15}{2} [2a_{1}+35]$[/tex]
[tex]$240=15a_{1}+535$[/tex]
[tex]-285=15a_{1}[/tex]
[tex]a_{1}=-19[/tex]
