Đáp án:
$1)
a, \dfrac{-2}{3}x^3y^5\\
b,\dfrac{-1}{5}x^5y^9\\
c, \dfrac{5}{3}x^3y^4\\
d, -x^3y^4\\
2)
a) A(x)= -4x^3 + 7x^2 + 6x-12\\
B(x) =2x^3+3x^2-9x+12\\
b, P(x) =-5x^3 + 7x^2 + 16x+12\\
Q(x) = -7x^5+2x^3+3x^2-9x-12\\$
Giải thích các bước giải:
$1)
a, - 6 x^2y^2.\dfrac{ 1}{9} xy^3=(-6).\dfrac{1}{9}.x^3y^5=\dfrac{-2}{3}x^3y^5\\
b, ( - x^4y ).xy^3 \dfrac{1}{5}.y^5 =(-1).\dfrac{1}{5}.x^5y^9=\dfrac{-1}{5}x^5y^9\\
c, 5 x^2y.\dfrac{1}{3} xy^3=5.\dfrac{1}{3}.x^3y^4=\dfrac{5}{3}x^3y^4\\
d, ( -2 x^2y ).xy^2 .\dfrac{1}{2}y=(-2).\dfrac{1}{2}.x^3y^4=-x^3y^4\\
2)
a) A(x)= -4x^3 + 7x^2 + 3x - 12 + 3x\\
=-4x^3 + 7x^2 + (3x +3x)-12\\
=-4x^3 + 7x^2 + 6x-12\\
B(x) = 2x^3 - 2x^2 + 12 + 5x^2 - 9x\\
=2x^3+(-2x^2+5x^2)-9x+12\\
=2x^3+3x^2-9x+12\\
b, P(x) = -5x^3 + 7x^2 + 8x + 12 + 8x\\
=-5x^3 + 7x^2 + (8x+ 8x)+12\\
=-5x^3 + 7x^2 + 16x+12\\
Q(x) = 2x³ - 2x² - 12 + 5x² - 9x - 7x⁵ \\
=-7x^5+2x^3+(-2x^2+5x^2)-9x-12\\
=-7x^5+2x^3+3x^2-9x-12\\$