Answer:
where y is positive.
The 2y in the denominator is not inside the fourth root
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Work Shown:
The idea is to get something of the form in the denominator. In this case,
To be able to reach the , your teacher gave the hint to multiply top and bottom by
For more examples, search out "rationalizing the denominator".
Keep in mind that only works if y isn't negative.
If y could be negative, then we'd have to say . The absolute value bars ensure the result is never negative.
Furthermore, to avoid dividing by zero, we can't have y = 0. So all of this works as long as y > 0.