`1,(2a - b)² - 4(a - b)²`
`= (2a - b)² - (2a - b)²`
`= (2a - b - 2a + b)(2a - b + 2a - b)`
`2) 9(a + b)² - 4(a - 2b)²`
`= (3a + b)² - (2a - 2b)²`
`= (3a + b - 2a + 2b)(3a + b + 2a - 2b)`
`3,25x² - 20xy + 4y²`
`= (5x)² - 2.5xy + (2y)²`
`= (5x - 2y)²`
`4,4x² - 12xy + 9y²`
`= (2x)² - 2.6xy + (3y)²`
`= (2x - 3y)²`
`5,9x^4 - 12x²y + 4y²`
`= (3(x)²)² - 12x²y + (2y)²`
`= (3x² - 2y)²`
`6,4x^4 - 16x²y³ + 16y^6`
`= (2(x)²)² - 16 x²y³ + ((2y)²)²`
`= (2x² - (2y)²)²`
Xin hay nhât !