# Homework Help: Excel: for maths problem

1. Jun 1, 2009

### sara_87

1. The problem statement, all variables and given/known data

I have a formula:
x=(y/s)^r

I am given data: 6 values for x and the corresponding 6 values for y.
I am to find the values of s and r.
I could take logarithms and make this formula linear then use linear regression (as in statistics) and do the method of least squares.
But i was told that using excel is much simpler (where i dont need to put this in terms of logarithms)
But how do i use excel for such a problem?

2. Relevant equations

3. The attempt at a solution

I typed in the values of x in the first excel column, and the values of y in the second. but then i got stuck. i have no idea how to and where to type in the formula.
Thank you

2. Jun 1, 2009

### MATLABdude

I believe you still need to linearize the formula. Consider what happens when you plot ln(y) versus ln(x). Excel can then give you an equation for the resulting plot of best fit. Using your linearized formula (what is it?), you should be able to easily extract s and r.

3. Jun 2, 2009

### sara_87

The linearized formula is:
ln(y)=(-1/r)ln(x)+ln(s)
so -1/r will be the gradient and ln(s) is the intercept of the plot ln(y) versus ln(x)
how do i plot this on excel?
Do i first type in the given values of x in column A and the given values of y in column B?

4. Jun 2, 2009

### sara_87

In column A, i typed the 6 values of x, and in B i typed the 6 values of y.
then in column C, i did: =log(A2) for the first one. and did the same for the rest.
in coulmn d, i did =log(B2) and the same for the rest.
The i did a scatter plot.
but this gave me a curve.
shouldnt it be a line?
And how can i then extract s and r?
thank you

5. Jun 2, 2009

### MATLABdude

I presume the values in column A begin in cell A2, and in column B begin in cell B2? Can you just list the values you were given for x and y?