a, \(=b\left(4+3a\right)\)
b, \(=ab\left(3+4a-2b\right)\)
c, \(=7\left(x+2\right)-xy\left(x+2\right)=\left(7-xy\right)\left(x+2\right)\)
d,\(=9y^2-\left(x+2\right)^2=\left(3y-x-2\right)\left(3y+x+2\right)\)
e, sửa đề \(=\left(2x-1\right)^2-9=\left(2x-4\right)\left(2x+2\right)=4\left(x-2\right)\left(x+1\right)\)
f, \(=3\left(3x^2-4x+1\right)=3\left(x-1\right)\left(3x-1\right)\)