Đáp án:
`a)12x³+6x`
`b)-x³y`
`c)10x²+5`
`d)-x²+x-1`
`e)3x^4-7x³-2x+9`
`f)-13x+25`
Giải thích các bước giải:
`a)x²(11x-2)+x²(x-1)-3x(-x-2)`
`=11x³-2x²+x³-x²+3x²+6x`
`=(11x³+x³)+(-2x²-x²+3x²)+6x`
`=12x³+6x`
`b)(4x²-3x).2xy+3x²(2y-3xy)`
`=8x³y-6x²y+6x²y-9x³y`
`=(8x³y-9x³y)+(-6x²y+6x²y)`
`=-x³y`
`c)(5x-1)(x+3)+(x-2)(5x-4)`
`=5x²+15x-x-3+5x²-4x-10x+8`
`=(5x²+5x²)+(15x-x-4x-10x)+(-3+8)`
`=10x²+5`
`d)(x-2)(x+2)-(x+1)(2x-3)`
`=x²-2²-(2x²-3x+2x-3)`
`=x²-4-2x²+3x-2x+3`
`=(x²-2x²)+(3x-2x)+(-4+3)`
`=-x²+x-1`
`e)4x³(x-1)-(x²-3)(x²+3)-(3x²+2)x`
`=4x^4-4x³-[(x^2)^2-3^2]-3x³-2x`
`=4x^4-4x³-(x^4-9)-3x³-2x`
`=4x^4-4x³-x^4+9-3x³-2x`
`=(4x^2-x^4)-(4x³+3x³)-2x+9`
`=3x^4-7x³-2x+9`
`f)(5-x)(5+x)-(x+1).3x-2x.(5-2x)`
`=5²-x²-3x²-3x-10x+4x²`
`=25-x²-3x²-3x-10x+4x²`
`=(-x²-3x²+4x²)-(3x+10x)+25`
`=-13x+25`