Question

which term of the AP 21,18,15... is zero?​

Answer 1

Answer:

$\sf\pink{answer} [tex]</h3><p> </p><p>first term of an AP = 21 common d/f = (18-21) = -3 </p><p>[tex]let \: tn = 0 \\ \\ tn0 = a + (n - 1)d \\ \\ 21 + (n - 1) - 3 \\ \\ 21 + 3n + 3 \\ \\ 21 - 3n + 3 \\ \\ 24 - 3n \\ \\ 3n = 24 \\ \\ n = 8 \\ \\ so \: 8th \: term \: is \: zero$