Question

U1, если U10=13,d=5
Арифм. Прогрессия

Answer 1

$U_{n} =U_{1} +d(n-1)\\\\U_{10} =U_{1} +5(10-1)\\\\13=U_{1} +5(10-1)\\\\U_{1}=13-5*9=13-45=-32$