Question

The common difference of an AP is -2.Find it's sum,if it's 1st term is 100&the last term is -10​

Answer 1

Answer:

Sum of terms in A.P is

n/2(a+l)

Here n=56

S=28(100-10)

=2520

hope it helps u...

please mark it as brainliest ANSWER..

Answer 2

Step-by-step explanation:

Here, a=100,tn=-10,d=-2.

tn=a+(n-1)d...formula

-10=100+(n-1)-2

(n-1)-2=-10-100

(n-1)-2=-110

n-1=-110/-2

n-1=55

n=55+1=56.

Sn=n/2[t1+tn]...formula

S56=56/2×[100+(-10)]

=28×90

S56=2520.

Sum is 2520.