Question

Thực hiện phép tính:
a)(6x²y-\(\dfrac{1}{2}\)xy+12y).(-\(\dfrac{1}{3}\)xy)
b)(2x+3-y).(2x-y)
c)3.(4x+1).(4x-1)-12.(4x²+1)

Answer 1

a) \(\left(6x^2y-\dfrac{1}{2}xy+12y\right)\left(-\dfrac{1}{3}xy\right)=-2x^3y^2+\dfrac{1}{6}x^2y^2-4xy^2\)

b) \(\left(2x+3-y\right)\left(2x-y\right)=4x^2+6x-2xy-2xy-3y+y^2=4x^2+y^2+6x-3y-4xy\)

c) \(3\left(4x+1\right)\left(4x-1\right)-12\left(4x^2+1\right)=3\left(16x^2-1\right)-48x^2-12=48x^2-3-48x^2-12=-15\)

Answer 2

b. (2x + 3 - y)(2x - y)

= 4x² - 2xy + 6x - 3y - 2xy + y²

= 4x² - 4xy + 6x - 3y + y²

= \(\left[\left(2x\right)^2-4xy+y^2\right]\) + (6x - 3y)

= (2x - y)² + 3(2x - y)

= (2x - y + 3)(2x - y)