Đáp án:
$\begin{array}{l}
B3)\\
a)0,2.{x^2}.{y^3}.5{x^4}{y^2}\\
= 0,2.5.{x^6}.{y^5}\\
= {x^6}.{y^5}\\
\Rightarrow Bậc:11\\
b)0,6.{x^4}{y^6}.z.\left( { - 0,2.{x^2}.{y^4}.{z^3}} \right)\\
= 0,6.\left( { - 0,2} \right).{x^4}.{y^6}.z.{x^2}{y^4}{z^3}\\
= - 0,12.{x^6}.{y^{10}}.{z^4}\\
\Rightarrow Bậc:20\\
c)\dfrac{1}{4}x{y^2}.\dfrac{1}{2}{x^2}{y^2}.\left( {\dfrac{{ - 4}}{5}y{z^2}} \right)\\
= - \dfrac{1}{{10}}.{x^3}.{y^5}.{z^2}\\
\Rightarrow Bậc:10\\
d){\left( { - \dfrac{1}{3}{x^2}{y^2}} \right)^2}.\left( { - 3{x^3}{y^4}} \right)\\
= \dfrac{1}{9}{x^4}{y^4}.\left( { - 3} \right){x^3}{y^4}\\
= - \dfrac{1}{3}{x^7}{y^8}\\
\Rightarrow Bậc:15\\
B5)\\
\left( { - 13{x^4}{y^m}} \right)\left( { - 3{x^n}{y^6}} \right)\\
= \left( { - 13} \right).\left( { - 3} \right).{x^4}.{y^m}.{x^n}.{y^6}\\
= 39.{x^{4 + n}}.{y^{m + 6}}\\
= 39.{x^{15}}.{y^8}\\
\Rightarrow \left\{ \begin{array}{l}
4 + n = 15\\
m + 6 = 8
\end{array} \right. \Rightarrow \left\{ \begin{array}{l}
n = 11\\
m = 2
\end{array} \right.\\
Vậy\,n = 11;m = 2
\end{array}$
