a) $2y(-x)^3.(-\dfrac{1}{2})xy^4$
$=-2yx^3.(-\dfrac{1}{2})xy^4$
$=(-2.-\dfrac{1}{2}).(x^3x)(yy^4)$
$=x^4y^5$
⇒ Biến $x^4y^5$, Bậc: $4+5=9$
b) $(\dfrac{13}{2}xy)^2.(-\dfrac{4}{13}xy^2z^3)$
$=\dfrac{169}{4}x^2y^2.(-\dfrac{4}{13})xy^2z^3$
$=(\dfrac{169}{4}.-\dfrac{4}{13})(x^2x)(y^2y^2)z^3$
$=-13x^3y^4z^3$
⇒ Biến $x^3y^4z^3$, Bậc $3+4+3=10$
c) $-\dfrac{1}{3}x^2y^3.\dfrac{3}{2}x^3y^2.(6x^2y^4)$
$=(-\dfrac{1}{3}.\dfrac{3}{2}.6)(x^2x^3x^2)(y^3y^2y^4)$
$=-3x^7y^9$
⇒ Biến $x^7y^9$, Bậc: $7+9=16$