Edexcel A2 C4 Mathematics June 2016 - Official Thread

wait so can you write it in both ways and its correct?????

what is the general formula for integrating a constant to a power of x (b^x)

sean are you an actual level student or are you at uni or something ?

No - the ln3x one isn't correct. That is why it seems strange to be able to choose what something integrates to - you can't.

I want to help people but at the same time I don't want to increase grade boundaries

Finished 2 out of 4 years of a maths degree.

Both lnx /3 +C and ln3x /3 +C are correct. Using log laws, ln3x = ln3 + lnx
ln3 is an arbritrary constant. With integration, you're adding an arbritrary constant C anyway, so both answers are correct, but would have different constants.

Haha true. the number of students on this thread to the number who will not put any work in and pull the grade boundaries down will still be very high, don't worry

Hey guys, I'm a little confused here, and am probably doing something stupid:

why isn't (4ln2)² = 5ln2?

This is my reasoning:

4ln2 = ln2^4

therefore (4ln2)(4ln2) = ln(2^4) * ln(2^4) = ln(2^4 + 2^4) = ln32 = ln2^5 = 5ln2

Surely? But my calculator says otherwise. What am I doing wrong? Thanks.

you're getting the product rule mixed up.

This part here is incorrect ln(2^4) * ln(2^4) = ln(2^4 + 2^4)

The rule goes ln(a) + ln(b) = ln(ab)

It is not true for the general case that ln(a) * ln(b) = ln(a+b)

Please could someone explain b) to me from last years paper???