# Thread: y= sqrt2x + 2sqrt2x

1. ## y= sqrt2x + 2sqrt2x

y= sqrt2x + 2sqrt2x

I need to find dy/dx,

When i differentiate each part I get the same result which I know is not correct,

y = 2x^-1/2 + 2(x^-1/2)

dy/dx = 1/2sqrtx + 1/2sqrtx

any help would be good

2. Originally Posted by drb11
y= sqrt2x + 2sqrt2x

I need to find dy/dx,

When i differentiate each part I get the same result which I know is not correct,

y = 2x^-1/2 + 2(x^-1/2) $\displaystyle \longleftarrow$ should be $\displaystyle y = (2x)^{1/2} + 2(2x)^{1/2}$
. . .

3. well using the power rule:

$\displaystyle f'(x)=nx^{n-1}$

We see in your problem:

$\displaystyle y= \sqrt{2x} + 2\sqrt{2x}$
1.
$\displaystyle y= (2x)^{1/2}+2(2x)^{1/2}$
2.
$\displaystyle y= (x)^{-1/2}+2(x)^{-1/2}$
3.
$\displaystyle y= x^{-1/2}+2x^{-1/2}$

4. [quote=Zanderist;475964]well using the power rule:

$\displaystyle f'(x)=nx^{n-1}$

We see in your problem:

$\displaystyle y= \sqrt{2x} + 2\sqrt{2x}$

$\displaystyle y= (2x)^{1/2}+2(2x)^{1/2}$

$\displaystyle y'= (x)^{-1/2}+2(x)^{-1/2}$ $\displaystyle \longleftarrow$ should be $\displaystyle y'= (2x)^{-1/2}+2(2x)^{-1/2}$

[\quote]

. . .

5. You are aware that $\displaystyle \sqrt{2x}+ 2\sqrt{2x}= 3\sqrt{2x}$ aren't you? Its derivative is $\displaystyle \frac{3}{2}\sqrt{2}x^{-1/2}= \frac{3}{2}\sqrt{\frac{2}{x}}$.

6. oops, it seems I made a mistake when posting the initial problem,

it was supposed to be:

y = sqrt2x + 2sqrtx

I know what the answer is but I don't know how to get there....

7. Originally Posted by drb11
oops, it seems I made a mistake when posting the initial problem,

it was supposed to be:

y = sqrt2x + 2sqrtx

I know what the answer is but I don't know how to get there....
$\displaystyle \sqrt{2x}+2\sqrt{x}=(\sqrt{2}+2)\sqrt{x}$

8. Sweet, thanks

9. Originally Posted by drb11

I know what the answer is but I don't know how to get there....
We see people writing this all the time. However you do not know what the answer is all you know is what it says at the back of the book. Which is not the same thing at all.

CB

10. Sorry captainblack sparrow. The reason I asked the question; for help on the process on how to get to the correct solution.I thought this was a math help forum ,obviously not, oh well, please revoke my membership. Feel free to feed upon my ego

11. Originally Posted by drb11
Sorry captainblack sparrow. The reason I asked the question; for help on the process on how to get to the correct solution.I thought this was a math help forum ,obviously not, oh well, please revoke my membership. Feel free to feed upon my ego