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# C3 finding roots question watch

1. Can someone pls help me with question 10 (last one) part B! I've been stuck on it for like 2 hours having no clue what to do ..
I opened solution banks it started from the gradient of the tangent being 1/q... How does it know???
2. (Original post by pondsteps)

Can someone pls help me with question 10 (last one) part B! I've been stuck on it for like 2 hours having no clue what to do ..
I opened solution banks it started from the gradient of the tangent being 1/q... How does it know???
Using the chain rule,
From this can find the gradient of the normal, thus the equation of the normal and substitute x=q.
3. (Original post by NotNotBatman)
Using the chain rule,
From this can find the gradient of the normal, thus the equation of the normal and substitute x=q.
Doesnt ln(3x) differentiate to give 3/3x ?
Oh never mind, that simplifies to 1/x
school boy error
4. (Original post by bobwibbles)
Doesnt ln(3x) differentiate to give 3/3x ?
Yes, which can be simplified to 1/x
5. Oh I think I got that thank u .. I found a similar question now (also part b) but also didn't known how to solve it 😭

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