(2x^2+3x)+(-x+4)=2x^2+3x-x+4=2x^2+2x
+4
(y^2-5y)+(5y-2y^2)=y^2-5y+5y-2y^2=y^2-2y^2=-y^2
(b^2-b+7)-(b^2+b+8)=b^2
-b+7-b^2-b-8=-2b-1
(8n^3-3n^2)-(7+8n^3-2n^2)=8n^3-3n^2-7-8n^3+2n^2=-n^2-7
(a^2+5a+4)-(a^2+5a-4)=a^2+5a+4-a^2-5a+4=8
(2x^2+3x)+(-x+4)=2x^2+3x-x+4=2x^2+2x
+4
(y^2-5y)+(5y-2y^2)=y^2-5y+5y-2y^2=y^2-2y^2=-y^2
(b^2-b+7)-(b^2+b+8)=b^2
-b+7-b^2-b-8=-2b-1
(8n^3-3n^2)-(7+8n^3-2n^2)=8n^3-3n^2-7-8n^3+2n^2=-n^2-7
(a^2+5a+4)-(a^2+5a-4)=a^2+5a+4-a^2-5a+4=8