determine o ultimo termo da p.a (5,7,2,11 ....an)sabendo que a soma de seus elementos e igual a 480
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a1 = 5
a2 = 7
a3 = 9 ( erro no exercicio dado )
r = 7 - 5 = 2 ***
an = 5 + ( n -1)2
an = 5 + 2n - 2
an = 3 + 2n *****
480 = ( 5 + 3 + 2n)*n/2
480/1 = ( 8 + 2n)*n/2
480/1 = ( 8n + 2n²/2
1 ( 8n + 2n² = 480 * 2
2n² + 8n = 960
n² + 4n = 480
n² + 4n - 480 = 0
delta = 16 + 1920 = 1936 = V1936 = 44
n = ( -4 +44)/2 =
n = 40/2 = 20 ****
a20 = 3 + 2 (20)
a20 = 3 + 40 = 43 ****
Pa [ 5,7,9,11,13,15,17,19,21,23,25,27,29,31,33,35,37,39,41,43]
a2 = 7
a3 = 9 ( erro no exercicio dado )
r = 7 - 5 = 2 ***
an = 5 + ( n -1)2
an = 5 + 2n - 2
an = 3 + 2n *****
480 = ( 5 + 3 + 2n)*n/2
480/1 = ( 8 + 2n)*n/2
480/1 = ( 8n + 2n²/2
1 ( 8n + 2n² = 480 * 2
2n² + 8n = 960
n² + 4n = 480
n² + 4n - 480 = 0
delta = 16 + 1920 = 1936 = V1936 = 44
n = ( -4 +44)/2 =
n = 40/2 = 20 ****
a20 = 3 + 2 (20)
a20 = 3 + 40 = 43 ****
Pa [ 5,7,9,11,13,15,17,19,21,23,25,27,29,31,33,35,37,39,41,43]
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