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# C1 MATHS HELP: Gradient watch

1. How do you decide whether to differentiate or to do 'change in y/change in x' to find the gradient?

For example, in the question below I know you can differentiate and whatnot to find the gradient but I don't see why you can't do change in y/change in x with the coordinates on the x-axis (despite the fact that 0 would be in the numerator)?

Attached Images

2. You can't use between the roots, because this doesn't give you the gradient of the normal(AB isn't perpendicular to the curve).
3. Because it is a normal to point A so it does not go through point b. So you only have point A to work with so you must therefore use differentiation.

Hope this helps

Posted from TSR Mobile
4. (Original post by ImNervous)
Because it is a normal to point A so it does not go through point b. So you only have point A to work with so you must therefore use differentiation.

Hope this helps

Posted from TSR Mobile
Ah that makes sense, thank you!

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Updated: December 28, 2014
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