# 009C Sample Midterm 2

This is a sample, and is meant to represent the material usually covered in Math 9C for the midterm. An actual test may or may not be similar.

Click on the  boxed problem numbers  to go to a solution.

## Problem 1

Evaluate:

(a)  ${\displaystyle \lim _{n\rightarrow \infty }{\frac {1}{{\big (}{\frac {n-4}{n}}{\big )}^{n}}}}$

(b)  ${\displaystyle \sum _{n=1}^{\infty }{\frac {1}{2}}{\bigg (}{\frac {1}{4}}{\bigg )}^{n-1}}$

## Problem 2

Determine convergence or divergence:

${\displaystyle \sum _{n=1}^{\infty }{\frac {3^{n}}{n}}}$

## Problem 3

Determine convergence or divergence:

(a)  ${\displaystyle \sum _{n=1}^{\infty }(-1)^{n}{\sqrt {\frac {1}{n}}}}$

(b)  ${\displaystyle \sum _{n=1}^{\infty }(-2)^{n}{\frac {n!}{n^{n}}}}$

## Problem 4

Find the radius of convergence and interval of convergence of the series.

(a)  ${\displaystyle \sum _{n=1}^{\infty }n^{n}x^{n}}$

(b)  ${\displaystyle \sum _{n=1}^{\infty }{\frac {(x+1)^{n}}{\sqrt {n}}}}$

## Problem 5

If  ${\displaystyle \sum _{n=0}^{\infty }c_{n}x^{n}}$  converges, does it follow that the following series converges?

(a)  ${\displaystyle \sum _{n=0}^{\infty }c_{n}{\bigg (}{\frac {x}{2}}{\bigg )}^{n}}$

(b)  ${\displaystyle \sum _{n=0}^{\infty }c_{n}(-x)^{n}}$