Question

soma dos dez primeiros termos da P.A. (4, 7, 10, ...) é igual a:

Answer 1

$\tt a_{10}=a_3+7r\\\tt a_{10}=10+7\cdot3\\\tt a_{10}=31\\\tt s_{10}=\dfrac{\diagup\!\!\!\!\!10\cdot(31+4)}{\diagup\!\!\!2}\\\tt s_{10}=5\cdot35\\\tt s_{10}=175$