If x^2+y^2=25 then find an expression for y''

Steps please, so i can compare to mine to see if i did this correct? I have a quiz tmr. I got (25/y^3) but i have a feeling i messed up on a sign somewhere.

Question

If x^2+y^2=25 then find an expression for y''

Steps please, so i can compare to mine to see if i did this correct? I have a quiz tmr. I got (25/y^3) but i have a feeling i messed up on a sign somewhere.

anonymous · Answer

i just need the steps for the second part where we find y'' and plug in the -25 at the end

anonymous · Answer

$$2xx'+2yy'=0$$
$$y'=-\frac{xx'}{y}$$ and then repeat

anonymous · Answer

im asking for specifics :3 lol i know the deriv. rules

zepdrix · Answer

Derivative with respect to x?

anonymous · Answer

no to y

anonymous · Answer

$$25-x ^{2} = y ^{2}$$
$$y = \sqrt{25 - x ^{2}}$$

zepdrix · Answer

no you're looking for derivative with respect to y. it says y'' at the top.
maybe you misunderstood what i was asking :o

zepdrix · Answer

respect blahhhh to x.. typo -_-

anonymous · Answer

the second derivative

zepdrix · Answer

|dw:1348804505243:dw|
hmm this is what i came up with