Answer
5
Work Step by Step
First 10 terms summed
$a_n = (-1)^n*(n+1)$
$n=1$
$a_n = (-1)^n*(n+1)$
$a_1 = (-1)^1*(1+1)$
$a_1 = -1*2$
$a_1=-2$
$n=2$
$a_n = (-1)^n(n+1)$
$a_2 = (-1)^2(2+1)$
$a_2=1*3$
$a_2=3$
$n=3$
$a_n = (-1)^n(n+1)$
$a_3 = (-1)^3*(3+1)$
$a_3=-1*4$
$a_3=-4$
$n=4$
$a_n = (-1)^n(n+1)$
$a_4 = (-1)^4*(4+1)$
$a_4=1*5$
$a_4=5$
$n=5$
$a_n = (-1)^n*(n+1)$
$a_5 = (-1)^5*(5+1)$
$a_5=-1*6$
$a_5=-6$
$n=6$
$a_n = (-1)^n*(n+1)$
$a_6 = (-1)^6*(6+1)$
$a_6=1*7$
$a_6=7$
$n=7$
$a_n = (-1)^n*(n+1)$
$a_7 = (-1)^7*(7+1)$
$a_7=-1*8$
$a_7=-8$
$n=8$
$a_n = (-1)^n*(n+1)$
$a_8 = (-1)^8*(8+1)$
$a_8=1*9$
$a_8=9$
$n=9$
$a_n = (-1)^n*(n+1)$
$a_9 = (-1)^9*(9+1)$
$a_9=-1*10$
$a_9=-10$
$n=10$
$a_n = (-1)^n*(n+1)$
$a_{10} = (-1)^{10}*(10+1)$
$a_{10}=1*11$
$a_{10}=11$
$(-2)+3+(-4)+5+(-6)+7+(-8)+9+(-10)+11$
$3-2+5-4+7-6+9-8+11-10$
$1+1+1+1+1$
$5$
