Question

find the sum of first 20terms of AP 3,7,11,15....using the formula​

Answer 1

Answer:

Hope it will help you...

Answer 2

$</p><p>\blue {\boxed{\underline {\underline {Sum \: = \: 79 .}}}}$

$</p><p>\orange {\underline {\underline {Step \: By \: Step \: Explaination- }}}$

$</p><p>\green{\boxed{\boxed{\underline {Sum \: = \: a \: + \: { n \: - \: 1 } \: d }}}}$

a = First term

n = Number of terms

d = Common Difference

$</p><p>\red{\boxed{\therefore{Sum \: = \: 3 \: + \: 19\: × \: 4 \: = \: 79}}}$