Solution:
we have been asked to find the product of (x+y+3)(x+y-4).
we will multiply term by term as below
[tex] (x+y+3)(x+y-4)=x(x+y+3)+y(x+y+3)-4(x+y+3)\\\\\ (x+y+3)(x+y-4)=x^2+xy+3x+xy+y^2+3y-4x-4y-12\\\\\text{Now take the like terms together and simplify we get}\\\\(x+y+3)(x+y-4)=x^2+y^2+2xy-x-y-12\\ [/tex]
Hence the the product of (x+y+3)(x+y-4) is [tex] x^2+y^2+2xy-x-y-12 [/tex]
