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# AS differentiation watch

1. The function h is given by h(x) = k/x^n where k and n are positive integers. The points (1,100) and (2,25) lie on the graph.

I) determine values k and n
2. (Original post by Custardcream000)
The function h is given by h(x) = k/x^n where k and n are positive integers. The points (1,100) and (2,25) lie on the graph.

I) determine values k and n
Well, you know that and

What can you do with this information?
3. (Original post by Zacken)
Well, you know that and

What can you do with this information?
Ahh I get it do you sub in one of the values of what k=
4. (Original post by Custardcream000)
Ahh I get it do you sub in one of the values of what k=
You have two equations in two variables. Simultaneous equations.

Although this one is very easy, the first equation should give you k directly and substituting it into the second gives you an equation which you can solve for n.
5. (Original post by Zacken)
You have two equations in two variables. Simultaneous equations.

Although this one is very easy, the first equation should give you k directly and substituting it into the second gives you an equation which you can solve for n.
K= 100
And n = 2 but I don't know how I show that
6. (Original post by Custardcream000)
K= 100
And n = 2 but I don't know how I show that
If, and we know that 1^anything = 1 then what can you say about k?

Then, re-arrange the second equation: , take logs of both side or spot n by inspection.
7. (Original post by Zacken)
If, and we know that 1^anything = 1 then what can you say about k?

Then, re-arrange the second equation: , take logs of both side or spot n by inspection.
Thanks for your help, I understand it now

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