91Ó°ÊÓ

Write a formula for the general term (the nth term of each arithmetic sequence. Then use the formula for \(a_{n}\) to find \(a_{20}\), the 20th term of the sequence Find the sum of the first 50 terms of the arithmetic sequence: \(-15,-9,-3,3, \ldots\)

Use the formula for the sum of the first n terms of a geometric sequence to solve. Find the sum of the first 14 terms of the geometric sequence: \(-\frac{1}{24}, \frac{1}{12},-\frac{1}{6}, \frac{1}{3}, \ldots\)

Write the first three terms in each binomial expansion, expressing the result in simplified form. $$\left(y^{3}-1\right)^{21}$$

Express each sum using summation notation. Use 1 as the lower limit of summation and i for the index of summation. $$\frac{1}{3}+\frac{2}{4}+\frac{3}{5}+\dots+\frac{16}{16+2}$$

Find the indicated sum. Use the formula for the sum of the first \(n\) terms of a geometric sequence. $$\sum_{i=1}^{8} 3^{i}$$

Express each sum using summation notation. Use 1 as the lower limit of summation and i for the index of summation. $$4+\frac{4^{2}}{2}+\frac{4^{3}}{3}+\dots+\frac{4^{n}}{n}$$

Find the indicated term in each expansion. $$(2 x+y)^{6} ; \text { third term }$$

Find the indicated sum. Use the formula for the sum of the first \(n\) terms of a geometric sequence. $$\sum_{i=1}^{6} 4^{i}$$

Write a formula for the general term (the nth term of each arithmetic sequence. Then use the formula for \(a_{n}\) to find \(a_{20}\), the 20th term of the sequence Find \(2+4+6+8+\dots+200,\) the sum of the first 100 positive even integers.

Find the indicated term in each expansion. $$(x+2 y)^{6} ; \text { third term }$$