AQA Core 3 1.04 Solving more advanced equations with e^x and ln(x)

[DanTheStripe]

Hi Jack, got a Core 3 mock literally in half an hour so just brushing up on some final knowledge.

I just wanted to question that at around 3:45 in the video you say ln(x+3)-ln(x) is equal to ln(x+3/x), using the second log law. However, I have been told that dividing by a variable isn't allowed and we should use factorisation instead, since if x is 0, then you would have ln(3/0). Does that rule only apply for trigonometry?

[nialackroyd]

how do you approach a question where e^ax is equal to 0, as ln0 can't be defined? E.g e^-2x - e^4x=0

[fraserlindsay]

when it says y=e^x when 2e^x +5e^-x = 7   what do you do please