Note: One reason for using WolframAlpha to handle some calculations is that you can sometimes see the steps involved, see additional information, make use of curated data in the calculation, etc.
After experimenting, WolframAlpha does not appear to understand FractionBox or SuperscriptBox or any other "two dimensional" "desktop published" input. That is the reason your query failed. Use "one dimensional" input form and you get your answer.
If you just must "desktop publish" your equations, to use square root symbols, numerators stacked over denominators, etc. then Put all that inside
=InputForm[...your two dimensional equations...]
which will undo the publishing format and mostly put your math into a form that WolframAlpha will understand.