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AS Level differentiation

I understand that 1/x would be dy/dx=-1/x^2
but
would xy=24 be dy/dx=x^-24 or x^-1 :s-smilie:?

The q is: find the equation of the tangent on the curve at the point indicated:
xy=24 where x=2
Reply 1
neither

you have y=24x=24x1y = \frac{24}{x} = 24x^{-1}
Reply 2
So when you differentiate you just multiply by the constant
Original post by TenOfThem
neither

you have y=24x=24x1y = \frac{24}{x} = 24x^{-1}


Thankyou so much!!! :smile:
I accidentely clicked the thumbs down when I went to click the thumbs up for your quote, it isn't letting me change it :s-smilie: ?
Thankyou anyway:biggrin:
Reply 4
no worries :smile:
Original post by jessica_anne_clu
Thankyou so much!!! :smile:
I accidentely clicked the thumbs down when I went to click the thumbs up for your quote, it isn't letting me change it :s-smilie: ?
Thankyou anyway:biggrin:


So... when dy/dx=-24x^-2, m=6 so m of the normal would be -1/6

where would I go from therE?
Reply 6
Did you need to find the equation of the tangent or of the normal?

Either way ... you know m

You know that x=2 ... what is y

Then you also have a point


Since you have a gradient and a point you should be able to find the equation
Original post by TenOfThem
Did you need to find the equation of the tangent or of the normal?

Either way ... you know m

You know that x=2 ... what is y

Then you also have a point


Since you have a gradient and a point you should be able to find the equation

trying to find the normal which is the reciprocal of the tangent changing the sign right? :smile:
Reply 8
yes you have the gradient

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