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# differentiate 3^x-1 watch

1. Hi
i need help in this question

How we differentiate y=3^x-1

I have done like that

1/y dy /dx = ln(3^x-1)

1/y dy/dx = (x-1)ln (3)
dy/dx = y (x-1) ln (3)
dy/dx = (3^x-1)(x-1)ln(3)

BUT MARK SCHEME
shows 3^x-1 (ln(3))

where I get wrong?
2. (Original post by Qer)
Hi
i need help in this question

How we differentiate y=3^x-1
or ?

I have done like that

1/y dy /dx = \ln (3^x-1)
1/y dy/dx = (x-1) \ln (3)
If

then

since and the derivative of a constant is 0.
3. (Original post by BobbJo)
or ?

If

then

since and the derivative of a constant is 0.
y=3^{x-1}
4. (Original post by Qer)

1/y dy /dx = ln(3^x-1)
It looks like you've not differentiated the RHS.
5. Alternative to implicit differentiation you could write and use chain rule
6. (Original post by Jarred)
It looks like you've not differentiated the RHS.
yeah

you are right

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