Câu `1:`
`a) (2x-3)^2 = (2x)^2 - 2 . 2x . 3 + 3^2 = 4x^2 - 12x + 9`
`b) (5/2-x)^2 = (5/2)^2 - 2 . 5/2 . x + x^2 = 25/4 - 5x + x^2`
`c) (2x+3y)^2 = (2x)^2 + 2 . 2x . 3y + (3y)^2 = 4x^2 - 12xy + 9y^2`
`d) (3x+2/3yz)^2 = (3x)^2 + 2 . 3x . 2/3 yz + (2/3yz)^2 = 9x^2 + 4xyz + 4/9y^2z^2`
`e) ((xy)/2 - x/3).((xy)/2 + x/3) = ((xy)/2)^2 - (x/3)^2 = (x^2y^2)/4 - (x^2)/9`
`f) (2x-y+z)^2 = (2x)^2 - y^2 + z^2 + 2 . 2x . y +2 . 2x . z - 2.y.z = 4x^2 - y^2 + z^2 + 4xy + 4xz - 2yz`
Câu `2:`
`a) 16x^2 + 24x +9 = (4x)^2 + 2 . 4x . 3 + 3^2 = (4x+3)^2`
`b) (x^2)/4 - 3x + 9 = (x/2)^2 - 2 . x/2 . 3 + 3^2 = (x/2 - 3)^2`
`c) 25/x^2 - 10/x + 1 = (5/x)^2 - 2 . 5/x . 1 + 1^2 = (5/x - 1)^2`
`d) 4x^4y^8 + ( x^2 y^4)^4 + 4`
` = (x^2 y^4)^2 +4x^4y^8 +4`
` = [(x^2 y^4)^2 ]^2 + 4x^4y^8 +2^2`
` = (x^4y^8)^2 + 2 . x^4 y^8 . 2 + 2^2`
` = (x^4y^8 + 2)^2`
`e) (2x-y)^2 + 2 . (2x-y) + 1 = (2x-y)^2 + 2.(2x-y).1 +1^2 = (2x-y+1)^2`
`f) (2x-4y)^2 + 4x-8y + 1`
` = (2x-4y) + 2 . (2x - 4y) . 1 +1^2`
` = (2x-4y + 1)^2`
