Question

An=4n-5 find 80th term of the ap and sum of 13th term​

Answer 1

Answer:

Hi!! Please check the image for your answer.

Answer 2

Answer:

80th term is 315

sum of 13 terms is

Step-by-step explanation:

An=4n-5

A80=4(80)-5

     =320-5

     =315

a=4(1)-5        a2= 4(2)-5  d=4

  =4-5               =8-5

  =-1                   =3

Sn=n/2{2a+(n-1)d}

   = 13/2{2(-1)+(13-1)4}

   = 13/2{48-2}

   =13/2*46

   =13*23

   =299