Question

which term of the AP 21,18,15,........is -30​

Answer 1

${\red{\huge{\mathcal{\star{Hey{\star}}}}}}$

${\blue{\huge{\boxed{\bf{18th}}}}}$

Steps-

a=21

d=-3

an=-30

an=a+(n-1)d

-30=21+(n-1)*-3

-30-21=-3n+3

-51-3=-3n

-54=-3n

n=18