Differentiation help (1 Viewer)

csi

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Hi guys,

I’m a bit stuck on this question:

Find the equation of the normal of the function f(x)=2x^2-5x+2 which is parallel to the line y=-1/4x+1/3.

Answer: 4x + 16y -23 = 0

Much appreciated if anyone could help!! Thanks:)
 

Drongoski

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Your problem is to find the point, P say, on the parabola y = f(x) where the normal passes. This normal has gradient -(1/4), so that the gradient of the tangent to the parabola at P is 4. You use this fact to find P, using f'(x) = 4.

 
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csi

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Your problem is to find the point, P say, on the parabola y = f(x) where the normal passes. This normal has gradient -(1/4), so that the gradient of the tangent to the parabola at P is 4. You use this to find P, using f'(x) = 4.

makes sense, thank you so much:)
 

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