Question 36·Hard·Linear Functions
The graph of the linear function is shown above.
If is linear, which equation defines ?
For linear-function transformation problems, rewrite the given graphed expression as a new function and compare it to . Substituting and simplifying lets you read how the transformation changes slope and intercept (here, flips slope sign, the outside factor 2 scales slope and intercept contribution from , and +5 shifts the intercept). Then match the slope/intercept you read from the graph to solve for and $b.
Hints
Name the graphed function
Let the graphed function be . Then .
Use slope-intercept form for
Assume . Substitute into and simplify to identify the slope and intercept of in terms of and .
Match to the graph
Find the slope and y-intercept of from the two intercepts on the graph, then set them equal to the slope and intercept you got from simplifying .
Desmos Guide
Enter two intercept points
From the graph, use the intercepts as points: and .
Confirm the equation of
In Desmos, plot the two points (-3,0) and (0,11/2).
Then type y=mx+b and adjust sliders so the line passes through both points, or compute directly from the two points. You should get slope and intercept for .
Solve back for
Let . Using , rewrite as .
Match slope and intercept with to solve for and , then write .
Step-by-step Explanation
Read slope and intercept from the graph
Let the graphed function be .
From the graph, crosses the x-axis at and the y-axis at .
So the slope of is
and the y-intercept is .
Write in slope-intercept form and transform
Because is linear, write .
Then
So the slope of is , and the y-intercept of is .
Match slope and intercept to solve for and
Match coefficients with the slope and intercept from the graph.
Slope:
Intercept:
Write
Substitute and into :