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# C3 Differentiation Problem watch

1. I'm stuck on question 7 part iii of this past paper
https://7c95ed1f832973eac0c6e1a52b08...20C3%20OCR.pdf

f(x) = ln x
g(x) = x^2 + 8

Find the gradient of the curve gf(x) where x = e^3

I can get to (ln x)^2 + 8 but every time I try to use the chain or product rule i always get it wrong
2. (Original post by JW22)
I'm stuck on question 7 part iii of this past paper
https://7c95ed1f832973eac0c6e1a52b08...20C3%20OCR.pdf

f(x) = ln x
g(x) = x^2 + 8

Find the gradient of the curve gf(x) where x = e^3

I can get to (ln x)^2 + 8 but every time I try to use the chain or product rule i always get it wrong
3. (Original post by JW22)
I'm stuck on question 7 part iii of this past paper
https://7c95ed1f832973eac0c6e1a52b08...20C3%20OCR.pdf

f(x) = ln x
g(x) = x^2 + 8

Find the gradient of the curve gf(x) where x = e^3

I can get to (ln x)^2 + 8 but every time I try to use the chain or product rule i always get it wrong
Wouldn't it just be 2*(lnx)*(1/x), and if you sub e^3 in you would get (2*(3lne))/e leading to 6/e^3 because lne = 1. I just did this in my head quickly I may have made a mistake
4. (Original post by Zacken)
Thanks

5. Full solutions are against forum guidelines.

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