# The sum of first 5 terms of an ap is 45 and that of its first 15 terms is 435. Find the sum of first n terms

2
by Shanaya888

2016-03-16T13:13:48+05:30

....(i)

...(ii)

On solving from eq.(i)

...(iii)

Putting 's value from eq.(iii) in eq.(ii) we get

...(iv)

Putting d's value from eq.(iv) in eq.(ii) we get

...(v)

Using eq.(iv) and eq.(v) we can get

2016-03-16T20:30:41+05:30
2n square - n is the sum of n terms