Question

calculati,stiind ca n apartine N* :

a) 2(-1)^n + 3(-1)^n-1 -4(-1)^n+4 - 5(-1)^n+1 + 6(-1)^n+2
b) 3(-1)^2n +5(-1)^2n+1 + 7(-1)^2n+2 + ..... +2015(-1)^2n+1008

Answer 1

a) n = numar par => 2-3+4-5+6 = 4

n = numar impar => -2+3-4+5-6 = -4

b) n = numar par => 3-5+7-9+.....-2013+2015+1008 = (-2)x1005 +2015+1008 = 1013

n = numar impar => -3+5-7+9......+2013-2015+1008 = 2x1005-2015+1008 = 1003