Question

If the general term of an AP is 9-5 n find the sum of first 10 terms of AP​

Answer 1

given

Ap - 7 ,11,15,19.

To find

sum of first 20 terms

solution

first term of ap is -7

common difference of Ap is

a2-a1=11-7=4

a3-a2=15-11=4

now formula of finding sum is

s(n)=n/2(2a+(n-1)*d

put value

=20/2(2(7)+(20-1)*4)

=10(14+76)

=10(90)

=900

hence,the sum of first 20 term is

\huge \underline \frak \pink {900}

900

Answer 2

your answer is 900 dear mate