Question 53·Medium·Equivalent Expressions
Which expression is equivalent to , where ?
For questions asking which expression is equivalent to a power with a fractional exponent, immediately use the rule and its reverse to rewrite everything with the same base and an explicit exponent. Convert every choice to , then compare those fractions directly to the given exponent—this avoids guessing and lets you decide quickly and accurately which expression is truly equivalent.
Hints
Connect fractional exponents and roots
Think about what a fractional exponent like means in terms of roots. How does the denominator of the fraction relate to the index (the small number) of a radical?
Rewrite radicals as powers of m
For an expression like , try rewriting it as . Do this for each answer choice so you can compare all of them in the same format.
Compare exponents
Once each option is written as , which one has the same exponent as ?
Desmos Guide
Graph the original expression as a function
In Desmos, type f(x) = x^(5/6) (this represents for ).
Graph each answer choice as a function
Create separate functions for each choice, for example:
gA(x) = nthroot(x^25, 10)forgB(x) = nthroot(x^5, 6)forgC(x) = nthroot(x^35, 12)forgD(x) = nthroot(x^10, 3)for
Compare the graphs to find the match
Look at the graphs of and each for . The function whose graph lies exactly on top of for all shown corresponds to the equivalent expression in the answer choices.
Step-by-step Explanation
Recall the rule for fractional exponents
A fractional exponent means a root. In general, for any positive number and integers and :
- .
So to compare expressions, it is helpful to rewrite radicals as powers (exponents) or powers as radicals using this rule.
Rewrite each answer choice using exponents
Use to turn each choice into a power of .
- Choice A: .
- Choice B: .
- Choice C: .
- Choice D: .
Now every option is written as .
Match the exponent to and select the equivalent expression
The original expression is , so we need the choice whose exponent is exactly .
From the exponents:
- A has exponent .
- B has exponent .
- C has exponent .
- D has exponent .
Only choice B has exponent , so the equivalent expression is choice B, .