//1 2 3 4 5 6 7 8.n 2 4 6 8 10 12 142n3 a a (+) 1+3+5+7+ , =a =d; .. =a =a+(1-1)d =a+d =a+(2-1)d =a+2d = a+(3-1)d.. . . . ...n = a+ (n-1)d n 2 5+8+11+14.. 383? a=5, d=8-5=11-8=3.. , n = 383 ,n =a+(n-1)d.. a+(n-1)d=383, 5+(n-1)3=383,5+3n-3=383, 3n =383-5+3,n=381, n =381/3 n=127 127 =383 n , a , p, d, n s, S=a+(a+d)+(a+2d)+..+(p-2d)+(p-d)+p ..1 s=p+(p-d)+(p-2d)+.(a+2d)+(a+d)+a ..2 s=(a+p)+(a+p)+(a+p)++(a+p)+(a+p)+(a+p),2s=n(a+p)s=n/2(a+p) (3), n =p=a+(n-1)d p ......3 , s=n/2{a+a+(n-1)d} s=n/2{2a+(n-1)d}

8 2n-1 1/2

n 5 7 22 (2p+1) 0 1+2+3+4+5++99=?

? ? 7+12+17+.. 30 ?