i need to derive a logarithmic equation in the form y=aloge(x+b)+c
given that it passes through the points (0,0) (12,20) (30,30)
it is a positive log with a horizontal asymptote x<0
can someone please help me work it out cos it is difficult!!!!!!!
i need to derive a logarithmic equation in the form y=aloge(x+b)+c
given that it passes through the points (0,0) (12,20) (30,30)
it is a positive log with a horizontal asymptote x<0
can someone please help me work it out cos it is difficult!!!!!!!
I presume you need to curve fit (0,0),(12,20),(30,30) such as,Originally Posted by asian5
Subsituting this into this equation yields,
---------
From equation 1 we have,
Substitute that into equation 2 and 3 thus,
Thus,
Divide these equation thus,
Cross multiply,
Now raise to that power,
Thus,
Thus,
Open sesame,
Thus,
Thus,
<to be countinued>
this gives you b.
Should be:Originally Posted by ThePerfectHacker
Thus,
Thus,
which has roots , and if we want
and to be real this rules out the first of these
roots and so , which is reassuringly in agreement
with the numerical result.
RonL
Yes I used the quadratic formula.Originally Posted by asian5
Substitute the value of into any two of the three equations
given at the top of The PerfectHackers first post, say:
this will leave you with a pair of linear equations in and .
or:
.
RonL