Question

If 4th term of an AP is -5 and its C.d is -3 .The sum of first 10 term is​

Answer 1

Answer:

a4 = -5 d= -3

a+3d= -5 ---- I

Substituting value of d in equation I

a+ 3(-3)= -5 => a= -5 +9 => a= 4

Now, n= 10

Sn= n/2 [2a+ (n-1)d]

S10 = 10/2 [2(4) + (10-1) -3]

= 5[ 8 -27]

=5[-19]

= -95