[tex]\displaystyle\bf\\a_{4} -a_{2} =36\\\\a_{5} -a_{3}=72\\\\\\\left \{ {{a_{1}\cdot q^{3} -a_{1}\cdot q=36} \atop {a_{1}\cdot q^{4} -a_{1}\cdotq^{2} =72 }} \right.\\\\\\:\left \{ {{a_{1} q^{2} \cdot (q^{2} -1)=72} \atop {a_{1} q \cdot (q^{2} -1)=36}} \right. \\------------\\q=2\\\\\\a_{1}=\frac{36}{q\cdot(q^{2}-1)} } =\frac{36}{2\cdot (2^{2}-1) } =\frac{18}{3} =6\\\\a_{6} =a_{1} \cdot q^{5} =6\cdot 2^{5} =6\cdot 32=192\\\\Otvet:a_{6}=192[/tex]