Question

5) Sendo a1=8 e a11=40, calcule a razão dessa p.a .

Answer 1

$an = ak + ( n - k ) * r \\ \\ 8 = 40 + ( 1 - 11 ) * r \\ \\ 8 = 40 - 10 * r \\ \\ 8 - 40 = -10 * r \\ \\ -32 / -10 = r \\ \\ \\ r = \dfrac{32}{10} => \dfrac{16}{5}$

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