Find the sum of consecutive terms of an arithmetic sequence Algebra II

Let u_n be a sequence defined as u_n=3+2n.

Calculate \sum_{k=1}^8u_k.

\sum_{k=1}^8u_k=96

\sum_{k=1}^8u_k=46

\sum_{k=1}^8u_k=122

\sum_{k=1}^8u_k=88

Let u_n be a sequence defined as u_n = \dfrac{-n}{4} + \dfrac{1}{2}.

Calculate \sum_{k=1}^8u_k.

\sum_{k=1}^{8} u_k =-5

\sum_{k=1}^{8} u_k =\dfrac{-35}{8}

\sum_{k=1}^{8} u_k =-13

\sum_{k=1}^{8} u_k =-8.5

Let u_n be a sequence defined as u_n = \dfrac{3n + 8n^2}{2n}.

Calculate \sum_{k=5}^{15}u_k.

\sum_{k=5}^{15} u_k = \dfrac{913}{2}

\sum_{k=5}^{15} u_k = 415

\sum_{k=5}^{15} u_k = 605

\sum_{k=5}^{15} u_k = \dfrac{1\ 026}{2}

Let u_n be a sequence defined as u_n = 4n - 7.

Calculate \sum_{k=3}^{8} u_k.

\sum_{k=3}^{8} u_k =90

\sum_{k=3}^{8} u_k =75

\sum_{k=3}^{8} u_k =125

\sum_{k=3}^{8} u_k =120

Let u_n be a sequence defined as u_n = \dfrac{5n}{2} + 2n + 6..

Calculate \sum_{k=1}^{16} u_k.

\sum_{k=1}^{16} u_k =708

\sum_{k=1}^{16} u_k =712

\sum_{k=1}^{16} u_k =\dfrac{3\ 009}{4}

\sum_{k=1}^{16} u_k =618

Let u_n be a sequence defined as u_n = 16 - \dfrac{4}{7}n.

Calculate \sum_{k=7}^{49} u_k.

\sum_{k=7}^{49} u_k =0

\sum_{k=7}^{49} u_k =86

\sum_{k=7}^{49} u_k =-42

\sum_{k=7}^{49} u_k =516

Let u_n be a sequence defined as u_n = -100 + 5n.

Calculate \sum_{k=0}^{19} u_k.

\sum_{k=0}^{19} u_k =-1\ 050

\sum_{k=0}^{19} u_k =0

\sum_{k=0}^{19} u_k =\dfrac{-1\ 995}{2}

\sum_{k=0}^{19} u_k =-1\ 000