a) \(\displaystyle -{2 \over 3}x{y^2}z.{\left( { - 3{{\rm{x}}^2}y} \right)^2} \)
\(\displaystyle = - {2 \over 3}x{y^2}z.9{{\rm{x}}^4}{y^2} \)
\(\displaystyle = \left( { - {2 \over 3}.9} \right)\left( {x.{x^4}} \right).\left( {{y^2}.{y^2}} \right).z \)
\(\displaystyle = - 6{{\rm{x}}^5}{y^4}z\)
b) \(\displaystyle {x^2}yz.{\left( {2{\rm{x}}y} \right)^2}z \)
\(\displaystyle = {x^2}yz.4{{\rm{x}}^2}{y^2}.z \)
\(\displaystyle = 4\left( {{x^2}.{x^2}} \right).\left( {y.{y^2}} \right).\left( {z.z} \right) \)
\(\displaystyle = 4{{\rm{x}}^4}{y^3}{z^2}\)
