Đáp án+Giải thích các bước giải:
`1) 1/9 - 2/3y^4 + y^8`
`= (1/3)² - 2.1/3.y^4 + (y^4)²`
`= (1/3-y^4)²`
`2) 1/4a² + 2ab² + 4b^4`
`= (1/2a)² + 2.1/2a . b² + (2b²)²`
`= (1/2a + 2b²)²`
`3) x^32 - 1`
`= (x^16)² - 1² `
`= (x^16 - 1)(x^16 + 1)`
`4) y^4 - 14y^2 + 49`
`= (y²)² - 2 . y² . 7 + 7²`
`= (y² - 7)²`
`5) 9/25x^4 - 1/4`
`= (3/5x²)² - (1/2)²`
`= (3/5x² - 1/2)(3/5x² + 1/2)`