Đáp án:
Giải thích các bước giải:
`a)`, \(x^2-9=\left(x-3\right)\left(x+3\right)\)
`b)` \(4x^2-25=\left(2x-5\right)\left(2x+5\right)\)
`c)` `x^6 - y^6 = (x^3 - y^3)(x^3 + y^3)`
`d)` \(9x^2+6xy+y^2\)
\(=9x^2+3xy+3xy+y^2\)
\(=3x\left(3x+y\right)+y\left(3x+y\right)\)
\(=\left(3x+y\right)^2\)
`e)` \(6x-9-x^2\)
\(=-\left(x^2-6x+9\right)=-\left(x^2-3x-3x+9\right)\)
\(=-\left(x-3\right)^2\)
`f)` \(x^2+4y^2+4xy\)
\(=x^2+2xy+2xy+4y^2\)
\(=x\left(x+2y\right)+2y\left(x+2y\right)\)
\(=\left(x+2y\right)^2\)
