??
Don't you think it would help to tell us what "rt" means? I might guess it means "root" but then which root? Square root probably- that is normally written as "sqrt(x)", not just "rt(x)". And "rt x/x^2" leaves it unclear whether you mean sqrt(x)/x^2 or sqrt(x/x^2).
In any case, you need to know that , that and that
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