What am I doing wrong for this question>

MAT 126.31: Calculus B Summer II 2021 Marissa Nobl: Homework: HW 1: Areas & The Definite Integral (Due 7 Score: 0 of 1 pt 4 1 of 9 (0 complete) V p 5.2.11 Express the following sum in sigma notation. Use 1 as the lower limit of summation and k for the index of summation. 1+2+3+...+15 Express the sum in sigma notation. X One or more of your responses is incorrect. X 15 Z k: 1 Your upper limit n is correct but your general term ak is incorrect. Recall the sigma notation for a nite sum. n 2 ak=a1+32+a3+"'+an-1+an k=1 The index of summation k indicates where the sum begins (at the number below the 2 symbol) and where it ends (at the number above 2). To express the given sum in sigma notation, determine the general term in terms of the index k, and the upper limit of summation, n. Note that the formula of the kth term is ak. OK Fntar \\Inllr angwnr in the, audit finlrls: and than nlink Chnnk Angwar