Question

Determine quantos múltiplos de 9 há entre 100 e 1000​

Answer 1

{108,117,... 981}

an=981

a1=108

r=117-108=9

n=?

$an=a1+(n-1)r \\981=108+(n-1)9 \\ 9n-9+108=981$

$9n=981-108+9 \\ 9n=882 \\ n=\frac{882}{9}\\ n=98$