Пошаговое объяснение:
1)-2x+x²+3x³-4x-2x²=3x³-x²-6x
3x2y²x-8x²y-3y²5x²=6x²y²-8x²y-15x²y²=-9x²y²-8x²y
2)(x²-5x-7)+(x-3x²+1)=x²-5x-7+x-3x²+1=-2x²-4x-6
(x²-5x-7)-(x-3x²+1)=x²-5x-7-x+3x²-1=4x²-6x-8
3)(5x²+8x-7)-(2x²-2x-12)=5x²+8x-7-2x²+2x+12=3x²+10x+5
4)5x-(3+2x-2x²)=2x²-7x+11
5x-3-2x+2x²-2x²+7x-11=0
10x=14
x=1.4
