(x-2)(x+2)-(x+1)(x-3) =（x^2-4)-(x^2+x-3x-3)=x^2-4-(x^2-2x-3)=x^2-4-x^2+2x+3=2x-1
(x-2)(x+2)-(x+1)(x-3) =x²-4-(x²-2x-3)=x²-4-x²+2x+3=2x-1
（X^2-4)-(x^2-2x-3)=2x-1
