Question

Find the sum of first 25 terms of following series whose n th term is given: (i) an =3+4n

Answer 1

For an AP, Sum of first n terms can be calculated as

S=n/2(first term+ nth term)

T(1)=7–3*1=4

T(25)=7–3*25=-68

So, sum is 25*(4–68)/2=25*(-32)=-800

Answer 2

1375 is required answer , I had complete explanation in attachment