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an = (1 - 3n) : 2
an > -10
(1 - 3n) : 2 > -10 /*2
1 - 3n > -20
-3n > -20 -1
-3n > -21 /:(-3)
n < (-21):(-3)
n < 7
Sa to wyrazy a1, a2,a3, a4,a5,a6
a1 = (1 - 3n) : 2
a1 = (1 -3*1):2
a1= (-2) : 2 = -1
a2 = (1 -3*2):2 = (-5):2 = -2,5
a3 = (1 -3*3):2 = (-8):2 = -4
a4 = (1 -3*4):2 = (-11):2 = -5,5
a5 = (1 -3*5):2 = (-14) :2 = -7
a6 = (1 -3*6):2 = (-17):2 = -8,5
a7 = (1 -3*7):2 = (-20):2 = -10 nie jest już rozwiazaniem
Odp. a1 = -1, a2 = -2,5; a3 = -4; a4 = -5,5 ; a5 = -7 ; a6 = -8,5