ewelina BLAGA POMOZCIE TO NA JUTRO!!!!!!!!!!!: Wyznacz wzor na n-ty wyraz iagu, ktorego suma n poczatkowych wyracow wyraza sie wzorem: a) S_n= 3n²-n b)S_n-n²-4n c)S_n=5n-n² 1 1 d)S_n= ----- n - ---- n² 2 4

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ewelina BLAGA POMOZCIE TO NA JUTRO!!!!!!!!!!!: pomoocyyyyyyyyy

danaole: ale jaki to ciąh

ewelina BLAGA POMOZCIE TO NA JUTRO!!!!!!!!!!!: arytmetyczny

%3Cpre%3E%3Cb%3Eewelina%20BLAGA%20POMOZCIE%20TO%20NA%20JUTRO!!!!!!!!!!!%3A%3C%2Fb%3E%20arytmetyczny%0A%3C%2Fpre%3E

Eta: można tak! a₁= S₁= 3*1-1= 2 S₂= 3*2² -2= 12-2=10 to oznacza że a₂ = 10-2=8 to r= 6 a_n= a₁ +(n-1)*r a_n= 2 +(n-1)*6 = 6n -4

Eta: Widać,że 1/ to arytmetyczny!

nalepek: A) lub tak: S_n=3n²-n S_n-1=3(n-1)²-(n-1) S_n-1=3n²-6n+3-n+1 S_n-1=3n²-7n+4 a_n=S_n-S_n-1 a_n=3n²-n-3n²+7n-4 a_n=6n-4

Eta: W b) zapisz porzadnie bo nie napisalas znaku = i nie wiem czy = - w c) podobnie jak w a) S₁= 5-1=4 to a₁=4 S₂= 10-4= 6 to a₂ = 4- 6= -2 S₃= 15-9=6 to a₃=0 wiec juz widac ,że to ciag arytm . a₁=4 r = -2 czyli a_n= A₁ +(n-1)*r = 4 +(n-1)*(-2) = -2n +6 sprawdzenie; S_n= (a₁ +a_n)/2 * n S_n =(4 -2n +6)/2* n = ( -2n² +10n)/2= - n² +5n = 5n -n² czyli ok!

Eta: Też tak można Nalepek!

ewelina BLAGA POMOZCIE TO NA JUTRO!!!!!!!!!!!: w b) jest tam =