(x+1)^ 2− (x+2) ^2− (x+3)^ 2+ (x+4) ^2

(x+1)²− (x+2)²− (x+3)²+ (x+4)²=
(x²+1)-(x²+4)-(x²+9)+(x²+16)=
x²+1-x²-4-x²-9+x²+16=
17-13=
4