Question

The sum of the fifth and sixth term of an AP is 30.If the third term is 5.Find the first term.

Answer 1

arithmetic progression formular: an=a + (n-1)d
first term a
2nd term: a+d
3rd term: a+2d
4th term: a+3d
5th term: a+4d
6th term: a+5d
(a+4d)+(a+5d)=30
2a+9d=30
 (a+2d=5)x2
 2a+9d=30
-2a+4d=10
        5d=20
d=4
a+2(4)=5
a+8=5
a=5-8=-3
1st term = -3