Arifmetik progressiin ehnii n gishuunii niilber

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  • 1. 799 n

2. n 3. n 4. a1. sn 5. . 6. 1+2+3+4+5+,,,+200=?. . S. : 7. 1+2+3+4+5+,,,+200=S.+++,,,+= s na1 a 2 a 3an. a1 a 2 a 3an+++,,,+= sn a1+++,,,+= s na n a n1 a n2 a1 8. 2: a1 a n a a n1 a3 a n2(+)+(+)+(+)+,,,+2 an a1s(+)=2.n a1 a n+ a.:=d+a n1an, 9. : a1 a n a1 a n1 a 2 a n1+=+d+=+= a2 a n2 a3 a n2 a n a1+d+=+=,,,=+a1 a ns(+)n=2.n. a1a n ns n= 2 10. n. a1a n n s n= 2nn 11. 1 an=4n+320.:n: a1a20 20s 20 ==a1a 20 10 2: 12. a1=413=7 a 20=803s 20 =a1a 20 10=78310=900 13. 21+3+5+,,,+17+19+21+19+17+,,,+3+1=?:a n =a1 n1 d19=1+(n1)2(n1)2=18n1=9n=10