Đáp án+Giải thích các bước giải:
Bài `2:`
`a) (2x-1)^2-2(x^2-3)`
`=(2x)^2-2.2x.1+1^2-2x^2+6`
`=4x^2-4x+1-2x^2+6`
`=(4x^2-2x^2)-4x+(1+6)`
`=2x^2-4x+7`
`b) (2x+1)(2x-1)-(x+4)^2`
`=(2x)^2-1^2-(x^2+8x+16)`
`=4x^2-1-x^2-8x-16`
`=(4x^2-x^2)-8x-(16+1)`
`=3x^2-8x-17`
`c) (2x-3)(3x+4)-6(x-2)^2`
`=6x^2-9x+8x-12-6(x^2-4x+4)`
`=6x^2-x-12-6x^2+24x-24`
`=(6x^2-6x^2)+(24x-x)-(12+24)`
`= 23x - 36`
`d) (x^4-3x^2+9)(x^2-3)+(3-x^2)^3`
`=x^6-3x^4-3x^4+9x^2+9x^2-27+27-27x^2+9x^4-x^6`
`=(x^6-x^6)-(3x^4+3x^4-9x^4)+(9x^2+9x^2-27x^2)-(27+27)`
`= 3x^4 -9x^2`
`e) (2x+1)^2+(2x+3)^2-2(2x+1)(2x+3)`
`=[(2x+1)-(2x+3)]^2`
`=(2x+1-2x-3)^2`
`= (-2)^2`
`=4`
