Bài 2: phân tích đa thức thành nhân tử
a) \(6x-3xy=3x\left(2-y\right)\)
b) \(x^2-3^2=\left(x-3\right)\left(x+3\right)\)
c) \(x^2+y^2+2xy-9=\left(x+y\right)^2-3^2=\left(x+y+3\right)\left(x+y-3\right)\)
Bài 3 : tìm x
a) \(x\left(x-2\right)-3\left(x-2\right)=0\)
\(\left(x-3\right)\left(x-2\right)=0\)
=> x ∈ {3;2}
b) \(\left(x+4\right)\left(x+4\right)-5x\left(x+4\right)=0\)
\(\left(x+4\right)\left(x+4-5x\right)=0\)
\(\left(x+4\right)\left(4-4x\right)=0\)
=> x ∈ {-4;1}