Question

Determine o primeiro termo de uma P.A em que A16=53 e R=42

Answer 1

$a_{16}=53\\ r=42\\ n=16\\a_1=?\\\\\\ a_n=a_1+(n-1)\times r\\\\\\ 53=a_1+(16-1)\times 42\to\\\\ 53=a_1+15\times 42\to\\\\ 53=a_1+630\to\\\\ 53-630=a_1\to\\\\ \boxed{a_1=577}$

Answer 2

Resposta:

$\textsf{Leia abaixo}$

Explicação passo-a-passo:

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

$\mathsf{ a_1=53-(16-1)\cdot42}$

$\mathsf{a_1=53-15\cdot42 }$

$\mathsf{a_1=53-630 }$

$\boxed{\boxed{\mathsf{a_1=- 577}} }$