~ Bạn tham khảo ~
`a, (x^3 + 8) - (x^2 - 4)`
`= (x+2)(x^2 - 2x + 4) - (x-2)(x+2)`
`= (x+2)(x^2 - 2x + 4 - x + 2)`
`= (x+2)(x^2 -3x+6)`
`b, (x^2 + y^2 - 5)^2 - 4(xy-2)^2`
`= (x^2 +y^2-5)^2 - (2xy-4)^2`
`= (x^2 +y^2-5-2xy+4)(x^2+y^2-5+2xy-4)`
`= (x^2+y^2-2xy-1)(x^2+y^2+2xy-9)`
`= [(x-y)^2 - 1]*[(x+y)^2 - 3^2]`
`= (x-y-1)(x-y+1)(x+y+3)(x+y-3)`
`c, 25(4x-3)^2-16(5x+7)^2`
`= (20x-15)^2 - (20x+28)^2`
`= (20x-15-20x-28)(20x-15+20x+28)`
`= -43(40x+13)`