1-guruh
Agar arifmetik progressiyada : a1=2, d=3 bo'lsa, a15 hadini toping.
a15=a1+14d
a15=2+14*3
a15=44
Agar arifmetik progressiyada a1=7,a16=67 bo'lsa, uning ayirmasini toping.
d=a16-a1
15d=67-7
15d=60
d=4
Agar geometrik progressiyada : b1=12,q=2 bo'lsa, uning dastlapki beshta hadini yozing.
12,24,48,96,192
Ushbu geometrik progressiyaning birinchi hadi va maxraji nimaga teng: -50,10,-2
b1=-50 va q=-5
2,6,18,.......... geometrik progressiyaning dastlapki 7 ta hadini toping.
b1=5,q=2,n=7
Javob:635
agar n=11 bo'lsa, 9;13;17,....... arifmetik progressiyaning dastlapki n hadi yig'indisini toping
a1=9 Sn=2a1+10d*11/2 formula
d=a2-a1=13-9=4
S11=2*9+10*4*11/2 =(18+40)*11/2=29*11=319
Javob: 319
b1=40,b2=20 bo'lsa,u cheksiz kamayuvchi bo'ladimi?
q=b2:b1
q=20/40
q=1/2
-1<q<1 -1<0,5<1 ha cheksiz kamayuvchi bo'ladi
cheksiz kamayuvchi geometrik progressiya yig'indisini toping: 128,64,2,..............
S=b1/1q
q=b2:b1=64/128=1/2
S=128/1*1/2
S=256