SOLUTION: If x∈Z, what is the sum of the digits of the value x such that √x+⁴√x=30?

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Question 1150463: If x∈Z, what is the sum of the digits of the value x such that √x+⁴√x=30?
Found 2 solutions by greenestamps, ikleyn:
Answer by greenestamps(13216)   (Show Source): You can put this solution on YOUR website!




Introduce a new variable to make it easier to see how to solve the problem.

Let y = x^(1/4)
Then y^2 = x^(1/2)

Then the equation is



or y =

y = -6 gives us x^(1/4) = -6, which is not possible.

y = 5 gives us x^(1/4) = 5, which makes x = 5^4 = 625.

ANSWER: The problem asks for the sum of the digits of x, which is 6+2+5 = 13.

Of course, if a formal algebraic solution is not required, the recognition that x^(1/4) is the square of x^(1/2) means we are looking for two integers, one the square of the other, whose sum is 30. That obviously is 5 and 25, which means x is 5^4 = 35^2 = 625.


Answer by ikleyn(52943)   (Show Source): You can put this solution on YOUR website!
.

The number x itself is 625,


and the sum of its digits (which is under the question) is 6+2+5 = 13.    ANSWER


            ANSWER.  13


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