so first factor it 1008=2*2*2*2*3*3*7 group them in similar pairs 1008=(2*2)(2*2)(3*3)*7 now remember we can do [tex] \sqrt{xy}= \sqrt{x} \sqrt{y} [/tex] so [tex] \sqrt{1008}= (\sqrt{2*2}) (\sqrt{2*2}) (\sqrt{3*3}) (\sqrt{7}) [/tex]= 2*2*3*[tex] \sqrt{7} [/tex]= 12√7
