✔ 最佳答案
1) (x^2+4x+4)-9y^2
= (x + 2)^2 - (3y)^2
= [ (x + 2) - (3y) ][ (x + 2) + (3y) ]
= (x - 3y + 2)(x + 3y + 2)
2) 25x^2-(9y^2-6y+1)
= (5x)^2 - [ (3y)^2-6y+1 ]
= (5x)^2 - (3y - 1)^2
= [ (5x) - (3y - 1) ][ (5x) + (3y - 1) ]
= (5x - 3y + 1)(5x + 3y - 1)
3) (x^2+6xy+9y^2)-16z^2
= [ x^2+6xy+(3y)^2 ] - (4z)^2
= (x + 3y)^2 - (4z)^2
= [ (x + 3y) - (4z) ] [ (x + 3y) + (4z) ]
= (x + 3y - 4z)(x + 3y + 4z)
4) 4x^2-(4y^2-4yz+z^2)
= (2x)^2 - [ (2y)^2-4yz+z^2 ]
= (2x)^2 - (2y - z)^2
= [ (2x) - (2y - z) ][ (2x) + (2y - z) ]
= (2x - 2y + z)(2x + 2y - z)