Use your graphs from problem 1-17 to answer the questions below.

1. How can the graph for the rule $y=2x+1$ be used to predict the result for an input ($x$-value) of $7$? How can the graph be used to predict the output ($y$-value) associated with an input of $3\frac{1}{2}$?

   Step 1 (a):

   Trace up from $x=7$. What is the $y$-value of the point?

   Step 3 (a):

   Trace up from $x=3.5$.

   Step 2 (a):

   Trace over to the $y$-axis to find the $y$-value.

   Step 4 (a):

   Trace over to the $y$-axis to find the $y$-value.

2. If you wanted an output of $7$ for the rule $y=-x+4$, what would you need as an input?

   Hint (b):

   What is the $x$-value when $y=7$?

3. For each of the rules in parts (a) through (e) of problem 1-17, where does the graph cross the $y$-axis? Describe any patterns you notice.

   Hint (c):

   Compare the points where the graphs cross the $y$-axis with their equations.