Question 243513
{{{(7x^2-xy+y^2)+(-x^2-7xy+5y^2)}}} Start with the given expression.



{{{7x^2-xy+y^2-x^2-7xy+5y^2}}} Remove the parenthesis.



{{{(7x^2-x^2)+(-xy-7xy)+(y^2+5y^2)}}} Group like terms.



{{{6x^2-8xy+6y^2}}} Combine like terms.



So {{{(7x^2-xy+y^2)+(-x^2-7xy+5y^2)=6x^2-8xy+6y^2}}}