to clarify when you say 1 - x^3 / x^1/2, do you mean 1 - (x^3 / x^1/2) or (1 - x^3) / (x^1/2)?
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If you mean 1 - (x^3 / x^1/2), then it would be (x^0)-(x^(5/2)), assuming x\(\ne\)0.
If you mean (1 - x^3) / (x^1/2), then it would be \(\frac{\sqrt{x}}{x}-x^{\frac{5}{2}}\). However, i cannot find a way to have this answer in the form of x^a-x^b.