`a) E=(2x + 3) - 2(2x + 3)(2x + 5) +(2x +5)^2`
`= 2x + 3 - (4x +6 )(2x + 5) + 4x^2 +20x + 25`
`= 2x + 3 - (8x^2 +12x + 20x + 30) +4x^2 +20x + 25`
`=4x^2 + 22x + 28 - 8x^2 - 12x - 20x - 30`
`= 4x^2 + 22x + 28 - 8x^2 -32x - 30`
`=-4x^2 - 10x - 2`
`b) F=(x^2+x+1)(x^2-x+1)(x^2-1)`
`=(x-1)(x+1)(x^2+x+1)(x^2-x+1)`
`=(x-1)^3(x+1)^3`
`=[(x^3)^2-1^2]`
`=x^6-1`
Xin hay nhất