Geometric sequence problems, thanks?

The sum of infinity of a geometric sequence is 18, and the sum to infinity of the squares of its terms is 162. Find the first term and common ratio.
Sol
Set m=r^2，，p=a(1)，q=p^2
1>m>0，1>r>0
p/(1－r)=18
p=18(1－r)……………….
q/(1－m)=162
q=162(1－m)
p^2=162(1－r^2)
324(1－r)^2=162(1－r^2)
2(1－r)^2=1－r^2
2r^2－4r+2=1－r^2
3r^2－4y+1=0
(3r－1)(r－1)=0
r=1/3 or r=1(reject)
a(1)=p=18*(1－1/3)=12