x²-5x-10=0   x1+x2=5x1x2=-10  2.2x²+7x+1=0x1+x2=-7/2x1x2=1/2 3.3x²-1=2x+53x²-2x-6=0x1+x2=2/3x1x2=-2 4.x（x-1）=3x+7x²-x=3x+7x²-4x-7=0x1+x2=4...