Could anyone please help me proving by definition that:
lim_(x,y)-->(2,1) f(x,y)=3
where f(x,y)= (x+y) / (x-y)
Thank you in advance.
The numerator and denominator are both continuous functions, so the only place where is not continuous is where the denominator . This does not occur at , so you can just use direct substitution.