Đáp án:
Phía dưới
Giải thích các bước giải:
Bài `3: `
`a) (x+2y)^2 = x^2+4xy+4y^2`
`b) (1/3x-4)^2 = 1/9x^2-8/3x+16`
`c) (y-3)(3+y)=y^2-9`
`d)(x+1/3)^3=x^3 + x^2+1/3x+1/27`
Bài `4: `
`a) 36x^3y^3-42x^2y^2`
`=6x^2y^2(6xy-7)`
`b)3x^4y^2+15x^2y-18xy`
`=3xy(x^3y+3x-6)`
`c) 27a^2(a-1)-9a^3(1-a)`
`=27a^2(a-1)+9a^3(a-1)`
`=(27a^2+9a^3)(a-1)`
`=9a^2(3+a)(a-1)`
`d)27x^3+8`
`=(3x+2)(9x^2-6x+4)`
`e)ax-bx+ab-x^2`
`=(ax+ab)-(x^2+bx)`
`=a(x+b)-x(x+b)`
`=(a-x)(a+b)`
`f)3(2x-1)-4x^2+4x-1`
`=3(2x-1)-(4x^2-4x+1)`
`=3(2x-1)-(2x-1)^2`
`=(3-2x+1)(2x-1)`
`=(4-2x)(2x-1)`
`=2(2-x)(2x-1)`
