Question

арифметическая прогрессия
a14=160, d=13
найдите a1=

Answer 1

$\displaystyle\bf\\a_{14} =160\\\\d=13\\\\a_{14} =a_{1} +13d\\\\a_{1}=a_{14}-13d=160-13\cdot 13=160-169=-9\\\\Otvet:a_{1} =-9$