August 2015

the question in the book is write the first four terms of the g.s. , if the sum of the first and fourth terms is 195 and the sum of the second and third terms is 60.
asub1+asub1r^3=195 (1)
asub1r+asub1r^2=60 (2)
Dividing (1) by (2)
r=1/2; r=4
Substitute in (2)
asubn=192; asub1=3
Therefore, the four terms are 3, 12, 48, 192.
My question is how did they get r=1/2 and r=4?