Question 980215
a, a, a^2, a^4.


{{{system(a^2-a=48,a^4-a^2=144)}}}


{{{(a^4-a^2)/(a^2-a)=144/48}}}


{{{((a^2-a)(a^2+a))/(a^2-a)=3}}}


{{{a^2+a=3}}}


{{{a^2+a-3=0}}}


{{{a=(-1+- sqrt(1+4*3))/2}}}


{{{highlight(a=(-1+- sqrt(13))/2)}}}, first term and also common ratio.