Question

Answer 1

Bài 1 :

\(a,\left(4x^2-8xy^2+1\right)\cdot\left(-\dfrac{1}{2}x^2y\right)\\ =-4x^2\cdot\dfrac{1}{2}x^2y+8xy^2\cdot\dfrac{1}{2}x^2y-\dfrac{1}{2}x^2y\\ =-2x^4y+4x^3y^3-\dfrac{1}{2}x^2y\\ b,\left(2x-y\right)\left(4x^2+2xy+y^2\right)\\ =\left(2x-y\right)\left[\left(2x\right)^2+2xy+y^2\right]\\ =\left(2x\right)^3-y^3=8x^3-y^3\\ c,\left(9a^2b+21ab^2-2ab\right):\left(-3a\right)\\ =-9a^2b:3a-21ab^2:3a+2ab:3a\\ =-3ab-7b^2+\dfrac{1}{3}b\)

Bài 2:

\(4x^2+6xy-1+3y\\ =\left(4x^2-1\right)+\left(6xy+3y\right)\\ =\left(2x-1\right)\left(2x+1\right)+3y\left(2x+1\right)\\ =\left(2x+1\right)\left(2x-1+3y\right)\)