Question

Find the sum of 51 terms of an ap whose 2nd and 3rd terms are 14 and 13 respectively

Answer 1

Answer:

a2=14

a+d=14............ (1)

a3=13

a+2d=13............ (2)

subtracting equation (1) from (2)

we get d=-1

putting the value of d=-1 in equation (1)

we get a=15

now a51=a+(n-1) d

a51=-35

s51=n/2(a+l)

=-510