Question

escreva a PA onde a5 = 20 e a20 = 50

Answer 1

a 5 = a 1 + (n - 1 ).r
a 5 = a 1 + (5 - 1 ).r
20 = a 1 + 4 .r
a 20 = a 1 +( n - 1) . r
50 = a 1 + 19 .r
-20 = -a 1 - 4 r(-1)
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30 = 15 r
15 r = 30
r = 30/15
r = 2
20 = a 1 + 4.r
20 = a 1 + 4 . 2
a 1 + 8 = 20
a 1 = 20 - 8
a 1 = 12
P.A(12,14,16,18,20,22,24,26,30,32,34,36,38,40,42,44,46,48,50