Question

Qual a razão de PA em que a1= -8 e a21=32? ​

Answer 1

$> \: resolucao \\ \\ \geqslant \: progressao \: \: aritmetica \\ \\ a1 = - 8 \\ a21 = 32 \\ \\ = = = = = = = = = = = = \\ \\ > \: a \: razao \: da \: pa \\ \\ a21 = a1 + 20r \\ 32 = - 8 + 20r \\ 32 + 8 = 20r \\ 40 = 20r \\ r = \frac{40}{20} \\ r = 2 \\ \\ \\ \geqslant \leqslant \geqslant \leqslant \geqslant \leqslant \geqslant \leqslant \geqslant$

Answer 2

$\mathsf{a_1=-8;~a_{21}=32;~n=21;~r=\,? }$

$\mathsf{ raz\tilde{a}o =\dfrac{a_n-a_1}{n-1} }$

$\mathsf{raz\tilde{a}o=\dfrac{32+8}{21-1} }$

$\mathsf{raz\tilde{a}o=\dfrac{40}{20} }$

$\boxed{\boxed{\mathsf{raz\tilde{a}o=2 }}}$