Prosze o pomoc. Matma Ciągi.
oblicz:
-2+3+8+...+98
ciąg arytm
a(1)=-2
r=5
a(n)=98
a(n)=a(1)+r(n-1)
98=-2+5(n-1)
98+2=5n-5
100+5=5n
105=5n / 5
21=n
S(n)=[( a(1) + a(n) ) / 2 ]* n
S(21)=1008
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ciąg arytm
a(1)=-2
r=5
a(n)=98
a(n)=a(1)+r(n-1)
98=-2+5(n-1)
98+2=5n-5
100+5=5n
105=5n / 5
21=n
S(n)=[( a(1) + a(n) ) / 2 ]* n
S(21)=1008