Which expression is equivalent to (x - 4)² - 5(x - 4) + 6? 

Researchers wanted to determine if listening to classical music can reduce math anxiety. They divided 100 students randomly into two groups and put them in identical rooms. Both groups completed a math test and a survey rating their level of math anxiety.  One group then listened to classical music for 10 minutes while the other group sat quietly. Both groups then took another math test, rated their level of math anxiety, and the researchers compared their results. Is this an observational study or an experiment?

In order for a school to purchase graduation gowns, the heights of all of the high school seniors are recorded. The heights are approximately normally distributed with a mean of 64.7 inches and a standard deviation of 4.267 inches. If a senior is selected at random, what is the probability that this student has a height that falls between 65 and 68 inches?

Consider the system of equations below.

(x + 1)² + (y - 4)² = 9   

x = 2

A deposit of $1250 is made into a savings account that earns 1.86% annual interest. The amount in this account at any time, t, in years,is modeled by A(t) = 1250(1.0186)^t. Which expression best models the equivalent monthly growth of the account?