Đáp án:
B9:
\(a)A = - \dfrac{{28}}{3}{a^{10}}{x^4}{y^7}\)
Giải thích các bước giải:
\(\begin{array}{l}
B9:\\
a)A = - \dfrac{1}{{27}}{a^3}.\left( { - 9} \right){x^2}y.\left( { - 8{a^6}} \right){y^6}.\dfrac{7}{2}a{x^2}\\
= - \dfrac{{28}}{3}{a^{10}}{x^4}{y^7}\\
b)HS: - \dfrac{{28}}{3}{a^{10}}\\
Bậc:4 + 7 = 11\\
B12:\\
a)M = A.B = - \dfrac{8}{{27}}{a^3}{x^3}{y^6}.4{x^6}{y^2}\\
= - \dfrac{{32}}{{27}}{a^3}{x^9}{y^8}\\
b)Bậc:9 + 8 = 17\\
B13:\\
a)M = A.B = \dfrac{3}{{250}}ax{y^2}.\left( { - 1000{a^3}} \right){x^3}{y^3}\\
= 12{a^4}{x^4}{y^5}\\
b)HS:12{a^4}\\
Biến:{x^4}{y^5}\\
Bậc:4 + 5 = 9
\end{array}\)
