" Life is not a problem to be solved but a reality to be experienced! "
© Copyright 2013 - 2025 KUDO.TIPS - All rights reserved.
an=a1+(n-1)d
Sn=1/2(a1+an)*n
DANE:
an=8-5n
OBL. S35
an=a1+(n-1)d
an=a1-d+nd------>d=-5 a1-d=8----->a1=8+d=8-5=3
a1=3 d=-5
a35=a1+34d=3-34*5=3-170=-167
s35=0,5*(3-167)*35=0,5*(-164)*35=-82*35=-2870
Odp. Suma trzydziestu pięciu początkowych wyrazów ciągu wynosi -2870.
a2=8-5*2=-2
r=3-(-2)=5
S35=3+(35-1)*5
S35=3+180-5
S35=178