Javob: n=49.
395. Agar:
1) a1=2 va d=5; 2) a1=-3 va d=2
bo’lsa, arifmetik progressiyaning dastlabki beshta hadini yozing.
396. n – hadining formulasi bilan berilgan quyidagi ketma-ketlik arifmetik progressiya bo’lishi isbotlang:
1) an=3-4n; 2) an=-5+2n;
3) an=3(n+1); 4) an=2(3-n).
397. Arifmetik progressiyada:
1) agar a1=2, d=3 bo’lsa, a15 ni toping;
2) agar a1=3, d=4 bo’lsa, a20 ni toping;
3) agar a1=-3, d=-2 bo’lsa, a18 ni toping;
4) agar a1=-2, d=-4 bo’lsa, a11 ni toping.
398. Arifmetik progressiyaning n- hadi formulasini yozing:
1) 1, 6, 11, 16, …; 2) 25, 21, 17, 13, …;
3) -4, -6, -8, -10, …; 4) 1, -4, -9, -14, ….
399. -22 soni 44, 38, 32, … arifmetik progressiyaning hadi. Shu sonning nomerini toping.
400. 12 soni -18, -15, -12, … arifmetik progressiyaning hadi bo’ladimi?
401. -59 soni 1, -5 … arifmetik progressiyaning hadi. Uning nomerini toping. -46 soni shu progressiyaning hadi bo’ladimi?
402. Agar arifmetik progressiyada:
1) a1=7, a16=67; 2) a1=-4, a9=0
bo’lsa, uning ayirmasini toping.
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