If (fx)=5x, what is f^-1(x)
1 answer:
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<h3>Answer: Choice B is correct</h3>
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Explanation:
Use a graphing tool like GeoGebra, Desmos, or your graphing calculator to plot each expression given as a separate y equation. Four parabolas should result.
The x intercept is the same as the root or zero of a function.
You should find that only choice B has a root thats larger than 4. That specific root being x = 7.
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A non-graphing approach:
You can use the quadratic formula or the factoring method to find the roots.
For choice A, it factors to (x+5)(x+6) = 0. The roots are x = -5 and x = -6 which aren't greater than 4. So we cross choice A off the list. Choices C and D are similar stories.
On the other hand, choice B factors to (x-7)(x+2) = 0 and it has roots of x = 7 and x = -2. This is another way to see why choice B is the answer.
Here are the steps for the quadratic formula for choice B
The quadratic formula is handy in case factoring is either not possible, or guess-and-check is too lengthy of a process. As you can probably tell, we could use the quadratic formula's results to help construct the factored form.