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# Alevel maths c3 help watch

1. How do you solve:
ln(x2+5x+6) - ln(x2+3x)=3
2. Use the rule:
ln(a) - ln(b) ≡ ln(a/b)
3. Thanks, however the answer states that the answer is x=2/e3 - 1??
4. (Original post by computerwizz)
How do you solve:
ln(x2+5x+6) - ln(x2+3x)=3
Applying log rules, you get ln[(x2+5x+6)/(x2+3x)]=3
Factorise (x2+5x+6) and you get (x+2)(x+3).
Factorise (x2+3x) and you get x(x+3)
Therefore x2+5x+6)/(x2+3x)=(x+2)/x as common factors eliminate.

ln[(x+2)/x]=3

3=ln(e^3)

This gives (x+2)/x = e^3.
EDIT: I accidentally multiplied this out. It should be 1+(2/x)=e^3. You can then rearrange.
5. (Original post by JemmaSimmons)
Applying log rules, you get ln[(x2+5x+6)/(x2+3x)]=3
Factorise (x2+5x+6) and you get (x+2)(x+3).
Factorise (x2+3x) and you get x(x+3)
Therefore x2+5x+6)/(x2+3x)=(x+2)/x as common factors eliminate.

ln[(x+2)/x]=3

3=ln(e^3)

This gives (x+2)/x = e^3.
x^2+2x=e^

x^2+2x-e^3 =0.

Thanks, however the answer states that it
is x=2/e3 - 1??
6. (Original post by jbiard)
ln(x^2+5x+6) - ln(x^2+3x)=3
ln( (x^2+5x+6)/(x^2+3x) ) =3
(x^2+5x+6)/(x^2+3x)=e^3

(x^2+5x+6)= e^3(x^2+3x)

(1-e^3)x^2 + (5-3e^3)x +6 = 0

X= 0.104791393 ,
Don't do this ever again. Never post full answers on TSR. Delete it before you receive a notice.
7. (Original post by JemmaSimmons)
Is that 2 over (e^3-1)?
Yes!
8. ln(x^2+5x+6) - ln(x^2+3x)=3
ln(X+3)(x+2)/x(X+3)=3
(X+2)/x=e^3
x+2=xe^3
2=xe^3-x
factorise and rearrange
9. (Original post by Rohit_Rocks10)
Don't do this ever again. Never post full answers on TSR. Delete it before you receive a notice.
woah why??
10. (Original post by jbiard)
woah why??
Much better to hint the person to the right answer rather than give them the full solution.
11. (Original post by TasnimCh)
ln(x^2+5x+6) - ln(x^2+3x)=3
ln(X+3)(x+2)/x(X+3)=3
(X+2)/x=e^3
x+2=xe^3
2=xe^3-x
factorise and rearrange

Thanks!
12. (Original post by RDKGames)
Much better to hint the person to the right answer rather than give them the full solution.
cool, but why would i get a notice?!
13. (Original post by jbiard)
cool, but why would i get a notice?!
Because it's part of the maths forum's rules not to give out a full solution unless OP doesn't understand after a suitable number of hints.
14. (Original post by computerwizz)
Thanks!
No worries dude
15. (Original post by RDKGames)
Because it's part of the maths forum's rules not to give out a full solution unless OP doesn't understand after a suitable number of hints.
yeah i just read the maths forum rules, didnt realise you werent aloud to give full worked solutions before, sorry!

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