Đáp án:
`1)A=-30`
`2)B=-175`
`3)C=-16x³-8x²+23x-8`
`4)D=-89`
`5)E=-19`
Giải thích các bước giải:
`1)A=3(x-1)²-(x+1)²+2(x-3)(x+3)-(2x+3)²-(5-20x)`
`=3(x²-2x+1)-(x²+2x+1)+2(x²-9)-(4x²+12x+9)-5+20x`
`=3x²-6x+3-x²-2x-1+2x²-18-4x²-12x-9-5+20x`
`=(3x²-x²+2x²-4x²)+(-6x-2x-12x+20x)+(3-1-18-9-5)`
`=-30`
`2)B=5x(x-7)(x+7)-x(2x-1)²-(x³+4x²-246x)-175`
`=5x(x²-49)-x(4x²-4x+1)-x³-4x²+246x-175`
`=5x³-245x-4x³+4x²-x-x³-4x²+246x-175`
`=(5x³-4x³-x³)+(4x²-4x²)+(-245x-x+246x)-175`
`=-175`
`3)C=-2x(3x+2)²+(4x+1)²+2(x³+8x+3x-2)-(5-x)`
`=-2x(9x²+12x+4)+16x²+8x+1+2x³+16x+6x-4-5+x`
`=-18x³-24x²-8x+16x²+8x+1+2x³+16x+6x-4-5+x`
`=(-18x³+2x³)+(-24x²+16x²)+(-8x+8x+16x+6x+x)+(1-4-5)`
`=-16x³-8x²+23x-8`
`4)D=(5x-2)²-(6x+1)²+11(x-2)(x+2)-16(3-2x)`
`=25x²-20x+4-(36x²+12x+1)+11(x²-4)-48+32x`
`=25x²-20x+4-36x²-12x-1+11x²-44-48+32x`
`=(25x²-36x²+11x²)+(-20x-12x+32x)+(4-1-44-48)`
`=-89`
`5)E=4x(x-3)-(x-5)²-3(x+1)²+(2x+2)²-(4x²-5)`
`=4x²-12x-(x²-10x+25)-3(x²+2x+1)+4x²+8x+4-4x²+5`
`=4x²-12x-x²+10x-25-3x²-6x-3+4x²+8x+4-4x²+5`
`=(4x²-x²-3x²+4x²-4x²)+(-12x+10x-6x+8x)+(-25-3+4+5)`
`=-19`
