Question 168·Hard·Nonlinear Functions
The graph of a polynomial function is shown above.
Which choice could be ?
When matching a polynomial to a graph, first read the x-intercepts and decide whether the curve crosses (odd multiplicity) or touches and turns (even multiplicity) at each intercept. Then use the left-right end behavior to rule out the wrong overall sign if needed. Finally, plug a labeled point (often the y-intercept) into your factored form to determine the constant multiplier and pick the exact expression.
Hints
Check the intercept behavior
At one x-intercept the graph crosses the x-axis, and at the other it just touches and turns around. Those two behaviors correspond to different powers of factors.
Build a factored form
Use the x-intercepts to write as , where the exponents depend on whether the graph crosses or bounces.
Use the labeled point
After you have the right factors, plug in the coordinate of the plotted point (the y-intercept is shown) to determine the constant multiplier .
Desmos Guide
Graph each option
Enter each answer choice as a separate function, for example:
Compare key features from the given graph
For each graph, check whether it:
- touches (bounces off) the x-axis at ,
- crosses the x-axis at ,
- passes through the point .
Select the matching expression
The correct choice is the one whose graph matches all of those features at the same time (both intercept behaviors and the y-intercept point).
Step-by-step Explanation
Use the x-intercepts and how the graph behaves there
The graph has zeros at and .
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At , the curve touches the x-axis and turns back down, so must have an even power (most simply, power ).
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At , the curve crosses the x-axis, so must have an odd power (most simply, power ).
So must have the form for some constant .
Use a point on the graph to find the scale factor
The graph shows the point on the curve.
Substitute into :
So .
Match to the answer choices
With , the function is , which matches one choice exactly.
Therefore, the correct choice is .