Question

Calcule o numero de Termoa de uma P.A sabendo que a1 = -14 , An = 19 e r = 3

Answer 1

$a_n=a_1+r(n-1)\\\\19=-14+3(n-1)\\\\19+14=3n-3\\\\33=3n-3\\\\33+3=3n\\\\36=3n\\\\n=\frac{36}{3}\\\\n=12$


A P.A. possui 12 termos.

Answer 2

Resposta:

$\textsf{Segue a resposta abaixo}$

Explicação passo-a-passo:

$\mathsf{ a_1=-14;~ a_n=19;~r=3;~ n=\,?}$

$\mathsf{a_n=a_1+(n-1)\cdot r }$

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

$\mathsf{ n=\dfrac{19+14}{3}+1}$

$\mathsf{n=\dfrac{33}{3}+1 }$

$\mathsf{ n=11+1}$

$\boxed{\boxed{\mathsf{ n=12}}}$