# Algebra Help

1. Aug 24, 2013

### DunWorry

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

I can't follow the math of the very last line.
It's really annoying me because I know its not supposed to be hard, I have tried multiplying top and bottom by k1+k2 and all kinds of rearranging but I'm not sure how they get from w1 - w2 / k1 - k2 = c (k1-k2) / (k1-k2)

Thanks

2. Aug 24, 2013

### Abhilash H N

Given ω1/k1=c
and ω2/k2=c right?
On cross multiplying we'll get ω1=ck1 , ω2=ck2..
Put these values in (ω12)/(k1-k2) And take c outside the bracket so as to arrive at c(k1-k2)/(k1-k2) which on simplification gives c ...

3. Aug 24, 2013

### Ray Vickson

They do not write
$$\omega_1 - \frac{\omega_2}{k_1} - k_2$$
as you claim. They write
$$\frac{\omega_1 - \omega_2}{k_1 - k_2}$$
which you can render in ASCII as (w1 - w2)/(k1-k2).