Verified answer

A1= -8

A20= 30

r= ?

An= A1+ (n-1).R

A20= A1 + 19.R

30= -8+19R

30+8=19R

38=19R

R=38/19

R=2

PA= (-8, -6, -4, -2, 0, 2, 4, 6, 8, 10, ...)

[tex]{\large\boxed{\boxed{  { \large \tt Bons~Estudos }}}}[/tex]

[tex] > \: resolucao \\ \\ \geqslant \: progressao \: \: aritmetica \\ \\ a1 = - 8 \\ an = 30 \\ n = 20 \\ \\ = = = = = = = = = = = [/tex]

[tex] > \: a \: razao \: da \: pa \\ \\ an = a1 + (n - 1)r \\ 30 = - 8 + (20 - 1)r \\ 30 = - 8 + 19r \\ 30 + 8 = 19r \\ 38 = 19r \\ r = \frac{38}{19} \\ r = 2 \\ \\ \\ \geqslant \leqslant \geqslant \leqslant \geqslant \leqslant \geqslant \leqslant \geqslant \leqslant \geqslant \geqslant [/tex]