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Mathematics 20 Online
OpenStudy (anonymous):

Show that equation (coming soon) has no (real-valued) solution.

OpenStudy (anonymous):

\[(dy/dx)^{2}+y ^{2}+4=0\]

OpenStudy (anonymous):

Can you re write it like\[\frac{ d ^{2}y }{ dx ^{2}}\]

OpenStudy (unklerhaukus):

i think \[\left(\frac{ \text d y }{ \text dx }\right)^2=y'^2\] is not the same as \[\frac{ \text d^2 y }{ \text dx^2 }=y''\]

OpenStudy (anonymous):

Does anybody know what my first step might be?

OpenStudy (unklerhaukus):

find dy/dx

OpenStudy (anonymous):

so solve for it.

OpenStudy (anonymous):

\[\frac{ dy }{ dx }=\sqrt{-y ^{2}-4}\]

OpenStudy (anonymous):

So already I can see that im going to have i in the answer. But i still need to prove it

OpenStudy (anonymous):

\[\sqrt{-1(x ^{2}+4)}\]

OpenStudy (anonymous):

\[i \sqrt{x ^{2}+4}\]Do you think that should be enough to satisfy the question

OpenStudy (anonymous):

@UnkleRhaukus plx take a look at my soln

OpenStudy (anonymous):

i just saw that i wrote c for y but if you ignore that am i correct

OpenStudy (anonymous):

x***

OpenStudy (unklerhaukus):

what you are doing makes sense to me , can you factor x^2 +4 ?

OpenStudy (anonymous):

No

OpenStudy (unklerhaukus):

hmm

OpenStudy (anonymous):

I guess this is it. Thanks for helping me get started. I probably just had to show that i is in the solution.

OpenStudy (unklerhaukus):

(x+i2)(x-i2)=x^2+4

OpenStudy (anonymous):

I didnt think of that. nice

OpenStudy (unklerhaukus):

i dont know what kind of answer they are looking for , i havent this type of question before

OpenStudy (anonymous):

I think we satisfied it by proving that the solution is riddled with the nonreal number i

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