Question

याद एक समातर श्रेढी में a = 15, d = -3 तथा an = 0 है, तो n का मान ज्ञात कीजिए।
If in an A.P., a = 15, d = -3 and an = 0, then find the value of n.​

Answer 1

it's a very easy question!

we know an=a+(n-1)d

substituting the values from question in above equation i.e.:-

0=15+(n-1)-3

then,0=15-3n+3

now,-15=-3n+3

further,-15-3=-3n

so,-18=-3n

-18/-3=n

now substraction sign will be cancelled

18/3=n

n=6