Solving a Differential Equation: dy/dt = t/(y + 1)

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SUMMARY

The differential equation dy/dt = t/(y + 1) with the initial condition y(2) = 0 can be solved by separating variables and integrating both sides. The integration yields (y + 1) dy = t dt, leading to y^2/2 + y = t^2/2 + C. To isolate y, one must multiply both sides by 2, complete the square on the left-hand side, and apply the initial condition to evaluate the constant C. The confusion regarding the square root and the constants arises from the need to complete the square before isolating y.

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Can someone help me find the solution for this

dy/dt = t/(y + 1) with initial condition y(2) = 0

here's what i have done so far
(y + 1) dy = t dt
y2/2 + y = t2/2 + C

i am confused on how to isolate y.
this is the solution
rmim21.gif
without using the initial condition. where did the + 1 in the square root and - 1 outside of the square root come from?
 
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First, multiply both sides by 2. Then complete the square on the LHS.
 
Don't forget, use y(2)=0, to evaluate C. (or c1).
 
After you've separated your variables and integrated both sides (which you have done correctly), multiply both sides by 2 to get rid of your coefficents and take the square root of both sides to solve for t. Then apply your condition.
 
TJ@UNF said:
After you've separated your variables and integrated both sides (which you have done correctly), multiply both sides by 2 to get rid of your coefficents and take the square root of both sides to solve for t. Then apply your condition.
Once you have multiplied both sides by 2, you will still have y^2+ 2y on the left side and just "taking the square root" won't give you y. Complete the square as Char. Limit said in the very first response to this thread.
 
Thanks for the help!
 

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