Find the sum of first 17 terms of AP whose 4th and 9th term - 15 and -30 respectively
Answers
Answered by
9
we have given 4th and 9th terms
means,
a+3d= -15
a+4d= -30
by subtraction method , we have
d=3
put value of d in eqn
a+12= -15
a= -27
now we have first term
a= -27,d=3,17th term is 21
sum of first 17 terms =n/2(a+l)
=17/2( -27+21)
=17/2( -6)
= -51
means,
a+3d= -15
a+4d= -30
by subtraction method , we have
d=3
put value of d in eqn
a+12= -15
a= -27
now we have first term
a= -27,d=3,17th term is 21
sum of first 17 terms =n/2(a+l)
=17/2( -27+21)
=17/2( -6)
= -51
Answered by
3
Answer:
Hope this helps you ✌️✌️
Attachments:
Similar questions