中括号6（X减3）的平房加上12（X加3）(X减3）减9（X减3）（X减1）中括号除以3（X减3）得几

原式=6(x-3)²/[3(x-3)]+12(x+3)(x-3)/[3(x-3)]-9(x-3)(x-1)/[3(x-3)]
=2(x-3)+4(x+3)-3(x-1)
=2x-6+4x+12-3x+3
=3x+9