[tex]48x^{6}+6x^{2}-26x^{3}[/tex]
You can list the factors of each term:
[tex]48x^{6}:2*2*2*2*3*x*x*x*x*x*x\\
6x^{2}:2*3*x*x\\
26x^{3}:-1*2*13*x*x*x[/tex]
The only factors that repeat are 2, x, and x. So your GCF for the whole term is [tex] 2x^{2} [/tex].
