Question

Aflati primul termen si ratia progresie aritmetice (an)n>=1.... info pe poză cu roșu semnat!

Answer 1

a1+r+a1+3r=16                      2a1+4r=16           a1+2r=8
a1(a1+4r)=28                         a1(a1+4r)=28       a1(a1+4r)=28

2r=8-a1                                   2r=8-a1                 2r=8-a1
a1(a1+16-2a1)=28                  a1(16-a1)=28        a²-16a+28=0

a1=2                 a1=14
r=2                    r=-3