`a,x² + y² + 2xy`
`= ( x+y )²`
`b,3x + x² + 2`
`= x² + x + 2x + 2`
`= x(x+1) + 2(x+1)`
`= (x+1)(x+2)`
`c,4x² + 8x + 4 `
`= 4(x² + 2x + 1 )`
`= 4(x+1)²`
`d,(2x + 3y)² + 4(2x+3y) +4`
`= (2x + 3y)² + 2.2(2x+3y) + 2²`
`= ( 2x+3y+2 )²`
`e,(5x-1)(5x+1)`
`= 25x² - 1`
`f,(4x-1)² + 2(4x - 1) + 1`
`= (4x-1+1)²`
`= 16x²`
`g,1 - 8xy + 16x²y²`
`= 16x²y²- 8xy+1`
`= ( 4x-1)²`
Xin hay nhất !