Question 315117
{{{x^2-xy-2y^2 }}}
={{{x^2+xy-2xy-2y^2 }}}
={{{(x+y)(x-2y)}}}




{{{2x^2-xy-y^2}}}
={{{2x^2+xy-2xy-y^2}}}
={{{(x-y)(2x+y)}}}

As there is no other common factor in the above exprssions, so HCF =1