Question

 2. (c+b)(c-b)-(5c^2-b^2)=

Answer 1

$(c+b)(c-b)-(5c^2-b^2)=c^2-b^2-5c^2+b^2=-4c^2$

Answer 2

 (c+b)(c-b)-(5c^2-b^2)=-4c^2