Self Check Expressions: two variables and fractional exponents

Questions
1

Anyone want to take a look at page 2? My CL seems to work to check an expression with two variables and whole number exponents or an expression with one variable and rational exponents, but not for an expression that has both. I’d like it to mark the following correct: 6x^(4/3)y^(1/2)

Thank you!

2

On check3, you’re testing the function with x=-10 and y=-1, but -1^(1/2) (= sqrt(-1)) is not going to be defined. If you change to all positive numbers, the check works correctly.

3

Of course! Thank you!