原式=[(x²-x-6)/(x-3)]÷[(x-3)/(x²-5x+6)]
={[(x+2)(x-3)]/(x-3)}÷{(x-3)/[(x-2)(x-3)]}
=(x+2)÷[1/(x-2)]
=(x+2)×(x-2)
=x²-4