Đáp án`+`Giải thích các bước giải:
` a) x^2/4 + 2xy + 4y^2`
`= (x/2)^2 + 2. x/2 . 2y + (2y)^2`
`= (x/2 + 2y)^2`
` b) -x^2 + 16x - 64`
`= -(x^2 - 16x + 64)`
`= -(x^2 - 2.x.8 + 8^2)`
`= -(x-8)^2`
` c) (2x+5)^2 -(x-9)^2`
`= (2x +5 - x +9)(2x + 5 + x - 9)`
`= (x + 14)(3x - 4)`
` d) 9(2x+3)^2 - 4(x+1)^2`
`= [3(2x+3)]^2 - [2(x+1)]^2`
`= {[3(2x+3)] - [2(x+1)]}{[3(2x+3)] + [2(x+1)]} `
`= (6x + 9 - 2x - 2)(6x + 9 + 2x + 1)`
` = (4x +7)(8x + 10)`
` e) 1 + 8x^6 y^3`
`= 1 + (2x^2 y)^3`
`= (1+2x^2 y)(1 + 2x^2 y + 4x^4 y^2) `
