1,2,4,7,11... maka bilangan ke -25 adalah
Matematika
SULASTRISpd
Pertanyaan
1,2,4,7,11... maka bilangan ke -25 adalah
2 Jawaban
-
1. Jawaban tsiqoh
1 2 4 7 11 16 22 29 37 46 56 67 79 92 106 121 137 154 172 191 211 232 254 277 301 -
2. Jawaban Sutr1sn0
1.......2..........4............7...........11,...
...+1.......+2.........+3........+4
.........+1........+1..........+1
a+b+c = 1
3a+b = 1
2a = 1
2a = 1
a = 1/2
3a + b = 1
3(1/2) + b = 1
3/2 + b = 1
b = 1 - 3/2
b = 2/2 - 3/2
b = -1/2
a + b + c = 1
1/2 + (-1/2) + c = 1
1/2 - 1/2 + c = 1
0 + c = 1
c = 1
Un = an^2 + bn + c
Un = 1/2 n^2 + (-1/2)n + 1
Un = 1/2 n^2 - 1/2 n + 1
n = 25
Un = 1/2 n^2 - 1/2 n + 1
U25 = 1/2 (25^2) - 1/2 (25) + 1
U25 = 1/2 (625) - 1/2 (25) + 1
U25 = 625/2 - 25/2 + 1
U25 = 600/2 + 1
U25 = 300 + 1
U25 = 301
Jadi bilangan ke-25 adalah 301