Đáp án: + Giải thích các bước giải:
`(7x-8)(7x+8)-10(2x+3)^2+5x(3x-2)^2-4x(x-5)^2`
`= (7x-8)(7x+8)-10(4x^2+12x+9)+5x(3x-2)^2-4x(x-5)^2`
`= (7x-8)(7x+8)-10(4x^2+12x+9)+5x(9x^2-12x+4)-4x(x-5)^2`
`= (7x-8)(7x+8)-10(4x^2+12x+9)+5x(9x^2-12x+4)-4x(x^2-10x+25)`
`= 49x^2-64-10(4x^2+12x+9)+5x(9x^2-12x+4)-4x(x^2-10x+25)`
`= 49x^2 - 64 - 40x^2 - 120x - 90 + 45x^3-60x^2+20x-4x^3+40x^2-100x`
`= 41x^3-11x^2-200x-154`
`(x^2-3)(x^2+3)-5x^2(x+1)^2-(x^2-3x)(x^2-2x)+4x(x+2)^2`
`= x^4 - 9 - 5x^2(x+1)-(x^2-3x)(x^2-2x)+4x(x^2+4x+4)`
`= x^4 - 9 - 5x^3 - 5x^2 - (x^2-3x)(x^2-2x)+4x(x^2+4x+4)`
`= x^4 - 9 - 5x^3 - 5x^2 - x^4 + 5x^3 - 6x^2 + 4x(x^2+4+4)`
`= x^4 - 9 - 5x^3 - 5x^2 - x^4 + 5x^3 - 6x^2 + 4x^3 + 16x^2 + 16x`
`= 4x^3 + 5x^2 + 16x -9`
