Question

bài 1 : làm tính nhân 

a) (2x - 1/4xy).(2 - 3x + 5x^2)

b)(3x^3 - 5x + 6x^2 - 1).(8 - x)

c) (5xy^2 - 2xy).(1/6x -8xy + 5/7x^2)

Answer 1

a) \(\left(2x-\dfrac{1}{4}xy\right)\left(2-3x+5x^2\right)=4x-6x^2+10x^3-\dfrac{1}{2}xy+\dfrac{3}{4}xy-\dfrac{5}{4}x^3y\)

b) \(\left(3x^3-5x+6x^2-1\right)\left(8-x\right)=24x^3-40x+48x^2-8-3x^4+5x^2-6x^3+x=18x^3+53x^2-3x^4-39x-8\)c) \(\left(5xy^2-2xy\right)\left(\dfrac{1}{6}x-8xy+\dfrac{5}{7}x^2\right)=\dfrac{5}{6}x^2y^2-40x^2y^3+\dfrac{25}{7}x^3y^2-\dfrac{1}{3}x^2y+16x^2y^2-\dfrac{10}{7}x^3y=\dfrac{101}{6}x^2y^2+40x^2y^3+\dfrac{25}{7}x^3y^2-\dfrac{1}{3}x^2y\)