4. write the radical expression in rational exponent form.
5√a

There's ambiguity here.  Either the original expression is "5 times the square root of a" or 5 is the "index of the root."

Then "5 times square root of a" would be  5a^(1/2), or
     1/2
5a

.  On the other hand, if you meant 5 to be the "index of the root," then the correct result would be

  1/5
a

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Horizontal change or the change of x