Question

determine o n° de termos da PA (-6,-9,-12.....-66)

Answer 1

$a_n=-66 \\ a_1=-6 \\ r=-9-(-6)=-9+6=-3 \\ n=? \\ \\ termo~~geral \\ \\ a_n=a_1+(n-1)r \\ \\ -66=-6+(n-1)(-3) \\ -66=-6-3n+3 \\ -66=-3-3n \\ -66+3=-3n \\ -63=-3n \\ \\ n= \frac{-63}{-3} \\ \\ n=21\mapsto~termos$

Answer 2

Resposta:

$\textsf{Segue a resposta abaixo}$

Explicação passo-a-passo:

$\mathsf{ n=\dfrac{a_n-a_1}{r}+1}$

$\mathsf{ n=\dfrac{-66+6}{-3}+1}$

$\mathsf{n=\dfrac{-60}{-3}+1 }$

$\mathsf{n=20+1 }$

$\boxed{\boxed{ \mathsf{ n=21}}}$