Differential Equations
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OpenStudy (anonymous):
Help me for a second time to answer my problem
Elimination of Constants
y=Cx+C^2+1
y=1+C1e^x+C2e^-2x
y=9x^2 +Bx+c
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OpenStudy (anonymous):
@ganeshie8 Can you please help me for a second time?
ganeshie8 (ganeshie8):
check the first equation once.... looks there is a typo ?
OpenStudy (anonymous):
ganeshie8 there is no typo that is different problems :)
OpenStudy (anonymous):
@dan815 Help me again? :)
OpenStudy (dan815):
go about it the same way as before
find y':
and y'':
Then try to find a linear combination where the constants dissappear
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ganeshie8 (ganeshie8):
y=Cx+C^2+1
y' = ?
OpenStudy (anonymous):
You're right I think my professor has a typo.
ganeshie8 (ganeshie8):
keep in mind, C is just a constant
OpenStudy (dan815):
are you sure its not cx^2 vanessa?
OpenStudy (anonymous):
dan815 yes i'm sure
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OpenStudy (dan815):
ok continue
OpenStudy (anonymous):
I think the x in Cx is a sub
OpenStudy (anonymous):
|dw:1403165946910:dw|
ganeshie8 (ganeshie8):
it helps if you can take a screenshot of equations and attach...
OpenStudy (anonymous):
@ganeshie8 Here's the photo
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ganeshie8 (ganeshie8):
that doesn't help much lol both look same !
ganeshie8 (ganeshie8):
lets skip this and work the remaining problems first... ?
OpenStudy (anonymous):
What problems?
ganeshie8 (ganeshie8):
remaining two problems :
y=1+C1e^x+C2e^-2x
y=9x^2 +Bx+c
ganeshie8 (ganeshie8):
start by creating the table :
y = 1+C1e^x+C2e^-2x
y' = ?
y'' = ?
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ganeshie8 (ganeshie8):
see if can you find the first and second derivatives ^^
OpenStudy (anonymous):
Ahm ok :)
OpenStudy (anonymous):
HAHAHA I can derived that XD Lol
ganeshie8 (ganeshie8):
good, find the derivatives :)
OpenStudy (anonymous):
*I can't XD
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OpenStudy (anonymous):
B'coz C is a constant XD
ganeshie8 (ganeshie8):
lol that makes our life easy
ganeshie8 (ganeshie8):
you can treat C as a number while differentiating
OpenStudy (anonymous):
hahaha You're right XD
ganeshie8 (ganeshie8):
give it a try
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ganeshie8 (ganeshie8):
y = 1+C1e^x+C2e^-2x
y' = (1+C1e^x+C2e^-2x)'
ganeshie8 (ganeshie8):
whats the derivative of 1 ?
OpenStudy (anonymous):
it's become 0 XD
ganeshie8 (ganeshie8):
see you do know how to differentiate it :) finish it off... !
ganeshie8 (ganeshie8):
y = 1+C1e^x+C2e^-2x
y' = (1+C1e^x+C2e^-2x)'
= 0 + ?
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OpenStudy (anonymous):
Lol I just can diffirentiate only 1 XD
OpenStudy (anonymous):
the game is over XD
ganeshie8 (ganeshie8):
game just started :P
OpenStudy (anonymous):
wahahaha So Solve it ! XD Don't pressure me XD
ganeshie8 (ganeshie8):
derivative of e^x is also easy :
\(\large (e^x)' = e^x\)
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ganeshie8 (ganeshie8):
e^x is the only function whose derivative equals the function itself.
OpenStudy (anonymous):
Then? What's next ? :D
ganeshie8 (ganeshie8):
lol this is your game - you will need to sweat :P
ganeshie8 (ganeshie8):
Also \(\large (e^{ax})' = ae^{ax} \)
OpenStudy (anonymous):
Wahaah Lol
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ganeshie8 (ganeshie8):
use them to find y' :
y = 1+C1e^x+C2e^-2x
y' = (1+C1e^x+C2e^-2x)'
= 0 + ?
OpenStudy (anonymous):
Can we subtract the 1 and 2 eq. ? XD
OpenStudy (anonymous):
(y)2 ?
y=2C1e^x+2C2e^-2x
Y'=C1e^x+(-2C2e^-2x)
OpenStudy (anonymous):
y'-y=C1e^x
OpenStudy (anonymous):
Am I right? @ganeshie8
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ganeshie8 (ganeshie8):
y' is right !
ganeshie8 (ganeshie8):
lets not rush to the final answer yet, cuz we have two constants c1 and c2.. that tells us that we need to differentiate it twice
OpenStudy (anonymous):
Ahh ok ! :)
ganeshie8 (ganeshie8):
y = 1+C1e^x+C2e^-2x
y' = 0 + C1e^x -2C2e^-2x = C1e^x - 2C2e^-2x
y'' = ?
ganeshie8 (ganeshie8):
differentiate y' again ^
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ganeshie8 (ganeshie8):
y' = C1e^x - 2C2e^-2x
y'' = ?