(2x+1)(x-1)-(x+1)(x-2)-10 =2x²-x-1-(x²-x-2)-10=x²-9=(x+3)(x-3)
原式=2X^2+X-2X-1-X^2-X+2X+2-10 =X^2-9 =(X+3)(X-3)
