Question

Calcule o a18 na P.A (-5,-3,-1....)

Answer 1

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$a_1=-5 \\ n=18 \\ r=-3-(-5)=-3+5=2 \\ \\ a_n=a_1+(n-1)r \\ \\ a_{18}=-5+(18-1)(2) \\ \\ a_{18}=-5+(17)(2) \\ \\ a_{18}=-5+34 \\ \\ a_{18}=29$

Answer 2

A18 = A1 + 17R

A18 = -5 + 17 * ( -2)

A18 = -5 + (-34)

A18 = (39) ✓