SOLUTION: Assume x > 0 and y > 0. If the square root of xy = 5, what is the smallest positive sum of 4x + y?

SOLUTION: Assume x > 0 and y > 0. If the square root of xy = 5, what is the smallest positive sum of 4x + y?

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Question 1059185: Assume x > 0 and y > 0. If the square root of xy = 5, what is the smallest positive sum of 4x + y?
Answer by Fombitz(32388) (Show Source): You can put this solution on YOUR website!
Define
You know that,

Substituting,

Now Z is a function of one variable.
Find the derivative and set it equal to zero to find the minimum.

So then,

and

You should technically calculate the second derivative and show that the extremum is a minimum.
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