Question 167·Medium·Equivalent Expressions
Which expression is equivalent to for positive real numbers and ?
For exponent-simplification questions like this, first isolate and simplify any grouped powers such as by distributing the exponent and using . Then rewrite the division of monomials as subtraction of exponents, being careful with signs, and cancel any common numerical factors early to keep the numbers small. Finally, convert any remaining negative exponents into positive ones by moving those factors to the denominator or numerator; doing this systematically avoids common sign mistakes and lets you match the result quickly to the answer choices.
Hints
Focus on the numerator first
Look at by itself. Use the rules and to distribute the power to each factor , , and .
Use exponent rules when dividing
After simplifying the numerator, you will have something of the form . Cancel the and then use to combine the exponents on and on .
Handle negative exponents at the end
Once you have simplified the exponents, if any variable still has a negative exponent, rewrite it as a positive exponent in the denominator using .
Desmos Guide
Enter sample values for the variables
In Desmos, define two sliders or constants for positive values, for example type a = 4 and b = 2, so you can substitute and into the expressions.
Evaluate the original expression numerically
On a new line, type the original expression using a and b:
((16*a^6*b^-2)^(1/4))/(2*a^-1*b^(3/2))
Note the numeric value that Desmos outputs for this expression.
Test each answer choice against the original value
For each option A–D, type the corresponding expression with a and b (for example, a^(5/2)/b^2 for one choice). Compare each output to the value from the original expression. The choice that always matches the original value (and still works if you change a and b to other positive numbers) is the correct equivalent expression.
Step-by-step Explanation
Rewrite and simplify the numerator
Start with the expression:
Apply the rule to the numerator:
Now apply to each power term in the numerator, keeping them in exponent form for now.
Compute the exponents in the numerator and set up the division
Evaluate each factor in the numerator:
- because .
- .
- .
So the whole expression becomes
Now cancel the common factor of in numerator and denominator, and use the rule for dividing powers with the same base, , to combine the and terms:
Simplify exponents and rewrite with positive exponents
Simplify the exponents:
- For : , so we get .
- For : , so we get .
Thus the expression becomes
Rewrite the negative exponent using :
So the expression is equivalent to .