Question

In a AP a=15,d=-3 ,an,=0 then find the value of n

Answer 1

Answer :-

Given :-

First term (a) = 15

Common difference (d) = -3

Last term (an) = 0

To Find :-

Number of terms n

Solution :-

$\huge{\boxed{\boxed{an \:=\: a \: +\:(n - 1)d}}}$

Putting values

» 0 = 15 + (n - 1)-3

» -15 = -3n + 3

» -15 - 3 = -3n

» -18 = -3n

» -18/-3 = n

» 6 = n

$\huge{\boxed{\boxed{n \:=\:6}}}$

Answer 2

Answer:6

Step-by-step explanation:

tn=a+(n-1)d

0=15+(n-1)-3

15=-3n+3

3n=15+3

n=18/3

n=6