6B
7C
8D
Bài 1:
\(a,=\left(2x-1\right)^2\\ b,=16y^3-2x^3-6x^2-6x-2\\ =2\left[8y^3-\left(x+1\right)^3\right]\\ =2\left(2y-x-1\right)\left(2y+2xy+2y+x^2+2x+1\right)\\ c,=2x^2+2x+5x+5=\left(x+1\right)\left(2x+5\right)\\ d,=\left(x-3y\right)^2-25z^2=\left(x-3y-5z\right)\left(x-3y+5z\right)\)
Bài 2:
\(A=y^3+3y^2+3y+1-y^3+3y^2-3y+1-6y^2+6=8\)