Question 140·Medium·Equivalent Expressions
Which expression is equivalent to , where and are positive?
For expression-equivalence questions with exponents, first rewrite any roots as fractional exponents so every part is in the same format. Then simplify systematically: distribute powers over products, use , and when dividing like bases, subtract exponents base by base. Keep fraction arithmetic organized (common denominators) and only look at the structure of exponents—this avoids messy numerical calculations and makes it much faster to match the correct answer.
Hints
Turn everything into exponents
Rewrite using a fractional exponent so that both the numerator and denominator are written only with exponents of and .
Handle the numerator carefully
Focus on . Use and then to find the new exponents on and .
Use the division rule for exponents
Once both numerator and denominator are written as powers of and , divide by subtracting exponents for each base separately: .
Simplify fractional exponents
Be careful when subtracting fractions like ; rewrite with denominator 4 before subtracting.
Desmos Guide
Evaluate the original expression numerically
In Desmos (calculator or graphing), type the original expression with specific positive values for and , such as and :
Record the numerical result that Desmos gives.
Evaluate each answer choice with the same values
On new lines in Desmos, type each choice with the same and values, for example:
- Compare each result with the value from the original expression; the choice that gives exactly the same number is the equivalent expression.
Step-by-step Explanation
Rewrite the square root using exponents
Start by rewriting the denominator using a fractional exponent.
- The square root .
So the expression becomes
Apply the power rule to the numerator
Use and on the numerator.
Now multiply the exponents:
- For :
- For :
So the numerator simplifies to
Now the whole fraction is
Divide by subtracting exponents
When you divide like bases with exponents, subtract the exponents: .
Handle and separately.
For :
For :
Putting these together, the simplified expression is
which corresponds to choice D.