Find d2y/dx2 at point (-2,1) for y^2-2x-4y-1=0

so i tired moving the xs and constants over:

y^2-4y=2x+1

but then I'm stuck...

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- Sep 10th 2009, 07:58 PMgenlovesmusic09d2y/dx2 at point (-2,1)
Find d2y/dx2 at point (-2,1) for y^2-2x-4y-1=0

so i tired moving the xs and constants over:

y^2-4y=2x+1

but then I'm stuck... - Sep 11th 2009, 12:26 AMchisigma
The explicit expression for is found resolving the algebraic equation...

(1)

... and we obtain...

(2)

Because is we have to choose in (2) the sign '-', so that is...

(3)

Kind regards

- Sep 11th 2009, 07:05 AMHallsofIvy
You don't need to solve for y, use "implicit differentiation".

Since , . Set y= 1 and solve for y'.

Do it again: . Set y= 1, and y' equal to the value you just found, and solve for y''.