Solving Separable Equations: How to Solve for Y in Terms of X

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SUMMARY

The discussion focuses on solving the quadratic equation derived from the expression y^2 - 2y = x^3 + 2x^2 + 2x + 3. Participants clarify that to solve for y in terms of x, one must rearrange the equation into the standard quadratic form ay^2 + by + c = 0, identifying c as -x^3 - 2x^2 - 2x - 3. The solution for y is then expressed as y = 1 ± sqrt(x^3 + 2x^2 + 2x + 4), confirming the quadratic nature of the equation. This highlights the importance of recognizing the coefficients in relation to the standard quadratic formula.

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davegillmour
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Ok, I'm having trouble with the last part of this problem. After solving for the constant C, I get:
y^2 - 2y = x^3 + 2x^2 +2x + 3

My question is, how do I solve this in terms of Y? The only instruction my book gives me is "To obtain the solution explicitly we must solve for y in terms of x. This is a simple matter in this case since the equation is quadratic in y" and then they jump to the solution:
y = 1 +/- sqrt(x^3 + 2x^2 +2x + 4)
 
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Well you said it yourself: it's a quadratic in terms of y.

Do you know how to solve quadratic equations?
 
dav2008 said:
Well you said it yourself: it's a quadratic in terms of y.

Do you know how to solve quadratic equations?


So would the expression x^3 + 2x^2 +2x + 3 be treated as the 'c' value in the quadratic eq?
 
Yep.

Remember that the quadratic equation let's you solve for a certain variable (we'll call it w here) when you have an equation in the form of aw^2+bw+c=0
 
Alright I got it, thanks a lot
 
davegillmour said:
So would the expression x^3 + 2x^2 +2x + 3 be treated as the 'c' value in the quadratic eq?

Actually, no. Since your equation is y^2 - 2y = x^3 + 2x^2 +2x + 3
and the quadratic is normally written ay^2+ by+ c= 0,
c= -x^3- 2x^2- 2x- 3.
 
Question: A clock's minute hand has length 4 and its hour hand has length 3. What is the distance between the tips at the moment when it is increasing most rapidly?(Putnam Exam Question) Answer: Making assumption that both the hands moves at constant angular velocities, the answer is ## \sqrt{7} .## But don't you think this assumption is somewhat doubtful and wrong?

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