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# C3 differentation with point of curve help !! watch

1. find the equation of the normal to the curve y=(x+4)/(x^2+1) at the point (0,4)
2. (Original post by yaaasminb)
find the equation of the normal to the curve y=(x+4)/(x^2+1) at the point (0,4)
Differentiate, find the gradient at the point, get the -ve reciprocal of the point, plug the point and the new gradient in your line construction method. Job done.
3. Differentiate the equation of y = (x+4)/(x^2+1) to get the gradient
dy/dx = 1/2x
Because you are finding the normal you will need to reciprocate to get 2x/1
Then substitute in the x value of 0 into the differentiated value.
m = 0
Use y - y(1) = m(x - x(1))
y - 4 = 0(x - 0)
You should get y = 4
4. (Original post by NatKH)
Differentiate the equation of y = (x+4)/(x^2+1) to get the gradient
dy/dx = 1/2x
Because you are finding the normal you will need to reciprocate to get 2x/1
Then substitute in the x value of 0 into the differentiated value.
m = 0
Use y - y(1) = m(x - x(1))
y - 4 = 0(x - 0)
You should get y = 4
1. You're incorrect,
2. Please don't post full solutions.
5. (Original post by RDKGames)
1. You're incorrect,
2. Please don't post full solutions.
Oh, sorry my bad
6. Have you learnt about the quotient, chain and product rules? Hint: One of those can be applied here Use it and see how far you get. Then post your working here and we can help you out more if needed.

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