# Calculus Question And Answer

[mage lang=”en|es|en” source=”flickr”]calculus question and answer[/mage]

**Can u answer this calculus question?**

If 1/x + 1/y = 3 and y(4) = 4/11 find y'(4) by implicit differentiation

Just take the equality given and differentiate it

(you can multiply by x*y first to make differentiation a little bit easier):

1/x + 1/y = 3

x*y*(1/x + 1/y )= 3*x*y

y + x = 3xy

(y + x)’ = (3xy)’

y’ + (x)’ = 3*(xy)’

y’ + 1 = 3*((x)’ * y + x*y’)

y’ +1 = 3*(y+x*y’)

Now set x=4:

y'(4) + 1 = 3*(y(4)+4*y'(4))

y'(4) + 1 = 3*(4/11+4*y'(4))

y'(4) + 1 = 12/11+12*y'(4)

11*y'(4) = 1-12/11 = -1/11

y'(4) = -1/121

**BC Calculus Sample Question 11 & 12**

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