Răspuns:
S=40200
Explicație pas cu pas:
a4-a2=4
a1+3r-(a1+r)=4
a1+3r-a1-r=4
2r=4
r=2
a1+a1+2r+a1+4r+a1+5r=30
4a1+11r=30
4a1+22=30
4a1=30-22
4a1=8
a1=2
S=a1+a1+r+a1+3r+......+a1+199r1=200a1+r1(1+2+....+199)=200*2+2*199*200/2
=200*2+200*199=200(2+199)=200*201
S=40200