Question

нпйдите а1 и d если а6=5.5 а21=17

Answer 1

d=(а21-а6)/15=(17-5, 5)/15=23/30
a6=a1+5d => a1=5, 5 - 5*23/30=5, 5 - 23/6=11/2 - 23/6=(33-23)/6=10/6=5/3