(x²-4x)²+7(x²-4x)+12
=[(x²-4x)+4][(x²-4x)+3]
=(x²-4x+4)(x²-4x+3)
=(x-2)²(x-1)(x-3)A的平方—B的平方+2/3B—1/9=a²-b²+2/3b-1/9
=a²-(b²-2/3b+1/9)
=a²-(b-1/3)²
=[a+(b-1/3)][a-(b-1/3)]
=(a+b-1/3)(a-b+1/3)