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# Year 13 Maths Help Thread Watch

1. (Original post by tiny hobbit)
The end bit should be dx + e

You can then equate coefficients of the x terms to find d.

The 24 is e
(Original post by NotNotBatman)
on the first line you just have +d, you should have +dx+e
I should have noticed that earlier! I've got the answer now, thank you!
2. Have i done something wrong ....

e^2x - e^x = 0
e^2x = e^x
lne^x = lne^2x
x=2x

??

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3. (Original post by kiiten)
Have i done something wrong ....

e^2x - e^x = 0
e^2x = e^x
lne^x = lne^2x
x=2x

??

Posted from TSR Mobile
looks fine;

now just find the value of x for which
4. (Original post by kiiten)
Have i done something wrong ....

e^2x - e^x = 0
e^2x = e^x
lne^x = lne^2x
x=2x

??

Posted from TSR Mobile
I think you should probably form a quadratic equation in e^x and go from there.
Doing it this way you may struggle to solve .
5. (Original post by B_9710)
I think you should probably form a quadratic equation in e^x and go from there.
Doing it this way you may struggle to solve .
But there is no 1 in the original equation?
6. (Original post by DylanJ42)
looks fine;

now just find the value of x for which

So zero?
7. (Original post by kiiten)
So zero?
perfect

as a matter of fact, going on what B_9710 said, how would you solve (just to make sure you know the method as you could be tested on it)
8. (Original post by kiiten)
So zero?

Yes, it is 0

What B_9710 was trying to say was you'd struggle to solve a similar equation involving a number, such as the one in his example, with the method you used. So if you knew how to solve it as a quadratic equation in ex it would be to your benefit.
9. (Original post by DylanJ42)
perfect
Thanks - i got confused because i did

x=2x
0 = 2x /x
0 = 2 ????

Is that wrong??

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10. (Original post by kiiten)
Thanks - i got confused because i did

x=2x
0 = 2x /x
0 = 2 ????

Is that wrong??

Posted from TSR Mobile
yea because x = 0 and so dividing by x creates a whole world of problems

from x = 2x just bring everything to the right of the equals sign(or the left, it doesnt matter) and get 0 = x
11. (Original post by DylanJ42)
yea because x = 0 and so dividing by x creates a whole world of problems

from x = 2x just bring everything to the right of the equals sign(or the left, it doesnt matter) and get 0 = x
2x / x isnt x though? (Bringing everything to the right of the equation)

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12. Different ques

???? I got y = 2 / ln

Where did i go wrong?

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Attached Images

13. (Original post by kiiten)
2x / x isnt x though? (Bringing everything to the right of the equation)

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sorry I worded that awfully, i mean "-x" from both sides of the equation to get 0 = x
14. (Original post by kiiten)
Different ques

???? I got y = 2 / ln

Where did i go wrong?

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For your other question, your equation is right - just solve it. If you had gone on to solve it and then put it back into the original question you would have been right - and you could have validated that for yourself rather than asking. Do not be afraid to try
15. (Original post by kiiten)
Different ques

???? I got y = 2 / ln

Where did i go wrong?

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first off,

also you cant say

that is similar to saying , it just doesnt make any sense.

I think the easiest way to do this question is to realise x and y must take the form (where n is just a number). So write , and go from there.

If not take equation 2 and "e" both sides (ive no idea what this step is actually called) to get then get in terms in x and sub into equation 1, then work out the quadratic which will follow

Edit: whoops you had the answer already, i didnt even notice
16. (Original post by SeanFM)

For your other question, your equation is right - just solve it. If you had gone on to solve it and then put it back into the original question you would have been right - and you could have validated that for yourself rather than asking. Do not be afraid to try
(Original post by DylanJ42)
first off,

also you cant say

that is similar to saying , it just doesnt make any sense.

I think the easiest way to do this question is to realise x and y must take the form (where n is just a number). So write , and go from there.

If not take equation 2 and "e" both sides (ive no idea what this step is actually called) to get then get in terms in x and sub into equation 1, then work out the quadratic which will follow

Edit: whoops you had the answer already, i didnt even notice
I dont already have the answer? unless you mean some of my working is correct.

Im confused - i rearranged equation 1 to get x. Then i subbed that into the 2nd equation to get

ln (e^5 - e^2 + y) + lny = 7
Now ? - do you bring lny to the other side then divide by ln?
17. (Original post by kiiten)
I dont already have the answer? unless you mean some of my working is correct.

Im confused - i rearranged equation 1 to get x. Then i subbed that into the 2nd equation to get

ln (e^5 - e^2 + y) + lny = 7
Now ? - do you bring lny to the other side then divide by ln?
You can't can't can't divide by ln on its own - as Dylan has already said in his post. lne^3 = 3 does not imply that e^3 = 3 / ln(....) because ln(...) without an argument is meaningless. Just like how you wouldn't divide sinx + cosx by sin(nothing) - it would be meaningless.

As Dylan has taken time to give you hints I will not proceed any further as it may be confusing to have input from multiple people. Good luck!
18. (Original post by SeanFM)
As Dylan has taken time to give you hints I will not proceed any further as it may be confusing to have input from multiple people. Good luck!
I was on the reply screen as you replied but you were first, it was my bad.
19. (Original post by kiiten)
I dont already have the answer? unless you mean some of my working is correct.

Im confused - i rearranged equation 1 to get x. Then i subbed that into the 2nd equation to get

ln (e^5 - e^2 + y) + lny = 7
Now ? - do you bring lny to the other side then divide by ln?
look on the right hand side of your page, you have . How do you get y on its own here?

Edit: wait i think you fluked getting this right
20. (Original post by DylanJ42)
look on the right hand side of your page, you have . How do you get y on its own here?
Ohhh so ....
e^lny = e^2
y = e^2

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