Question

Последовательность (сn) задана условиями: с1 = 2 и сn = cn-1 + 2 при n>1. Найти с12.​

Answer 1

$\displaystyle\bf\\c_{1} =2\\\\c_{n} =c_{n-1} +2\\\\c_{2} =c_{1} +2=2+2=4\\\\c_{2} =c_{1} +d\\\\d=c_{2} -c_{1} =4-2=2\\\\c_{12}=c_{1} +11d=2+11\cdot 2=2+22=24\\\\Otvet:c_{12} =24$