Difficulty to find this integral

DDarthVader
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Homework Statement


Hi! I'm not being able to solve this integral: \int \sqrt{2ax}\; dx We have started with integral yesterday and I don't know much yet.



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The Attempt at a Solution


This is what I tried to solve the integral
\int \sqrt{2ax}\; dx = \int u^{\frac{1}{2}}\; du = \frac{2}{3}{}u^{\frac{3}{2}}=\frac{2}{3}\sqrt[3]{(2ax)^2}
 
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Assuming that a is a real constant,
\int \sqrt{2ax}\; dx = \int \sqrt{2a}\sqrt x\; dx= \sqrt{2a} \int \sqrt x\; dx
Since \sqrt x is the same as x^{\frac{1}{2}}, you can easily find its integral, and then multiply by \sqrt {2a} to get the final answer.
 
DDarthVader said:

The Attempt at a Solution


This is what I tried to solve the integral
\int \sqrt{2ax}\; dx = \int u^{\frac{1}{2}}\; du = \frac{2}{3}{}u^{\frac{3}{2}}=\frac{2}{3}\sqrt[3]{(2ax)^2}
When you use a substitution, as you obviously did above, you need to write down what the substitution is. IOW, you should have u = <...> somewhere close by.

Also, u3/2 = ##\sqrt{u^3}##, not ##\sqrt[3]{u^2}##, which is what you had.
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
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