Question 1189826
the first term of a G.P is x and 3rd term is y.  
Find an expression for the common ratio in terms ]
of x and y.</pre>

So the sequence is like this

__<u>x</u>__, ___, __<u>y</u>__,...

{{{r=matrix(1,2,2nd,term)/matrix(1,2,1st,term)}}}{{{""=""}}}{{{r=matrix(1,2,3rd,term)/matrix(1,2,2nd,term)}}}{{{""=""}}}{{{x*r}}}{{{""=""}}}{{{y/r}}}

{{{x*r^2}}}{{{""=""}}}{{{y}}}
{{{r^2}}}{{{""=""}}}{{{y/x}}} 
{{{r}}}{{{""=""}}}{{{"" +- sqrt(y/x)}}}</pre>
The 1st and 3rd term of a G.P are 8 and 18 respectively 
and the common ratio is positive, find the common ratio.<pre>
Plug in x=8 and y=18 in that and solve for r, using only 
the + of ±.

Edwin</pre>