... xxx: jesli w pewnym ciagu arytm. a5=19 oraz a9=35 to wzor ogolny tego ciagu ma postac

xxx: ?

KUZDE: a₉ = a₅ + 4r 35 = 19 + 4r =. r = 4 a₅ = a1 + 4r => a1 = 19 − 16 = 3 a_n = 3 + ( n − 1 ) 4 a_n = 4n −1

Bizon: a₉−a₅=4r 4r=16 r=4 a₅=a1+4r 19=a₁+16 a₁=3 a_n=a₁+(n−1)r a_n=3+(n−1)4 a_n=4n−1

maniuś:

	a9−a5		16
r=		=		=4
	9−5		4

a_n= a₅+(n−5)*r = 19+4n−20 = 4n−1