(-3x²y³)=-3x²y³（9a²b-6ab²）÷（3ab）=3a-2b如果（-x+3）²=x²=ax+9 则：x²-6x+9=x²6x=9x=3/2因：x²=ax+99/4=(3/2)a+99=6a+366a=27a=9/2