(x+4)(x-1)-(x+2)(x-3)其中x=负3分之1=（x平方+4x-x-4）-（x平方-3x+2x-6）是用什

多项式乘法法则
(a+b)(c+d)=ac+ad+bc+bd
=ac+bc+ad+bd
(x+4)(x-1)-(x+2)(x-3)
=x²+4x-x-4-(x²-3x+2x-6)
=4x+2
=4×(-1/3)+2
=2/3