x的值是何时（3x+2）分之（9x方-4）的值为零
9x^2-4=0
x^2=4/9
x=±2/3
x=-2/3时,分母3x+2=0无意义
所以x=2/3时（3x+2）分之（9x方-4）的值为零
{[a(a-8)]/(a^2-4)+3/(a-2)}÷[(a^2-6a+9)/(a+2)[
={[a(a-8)]/(a^2-4)+3(a+2)/(a^2-4)}÷[(a^2-6a+9)/(a+2)]
={(a^2-5a+6)]/(a^2-4)}÷(a^2-6a+9)*(a+2)
={(a-2)(a-3)]/[(a+2)(a-2)}÷(a-3)^2*(a+2)
=(a-3)/(a+2)÷(a-3)^2*(a+2)
=1/(a-3)