.
Consider this function, defined on the number line for all real numbers
/ 0 if x is irrational,
|
f(x) = <
|
\ 1 if x is rational.
This function is discontinued at every point on the number line.
Next consider function g(x) = 1 - f(x).
This function is discontinued at every point on the number line, too.
But the sum of these two functions f(x) +g(x) = f(x) + (1 - f(x)) == 1 is identically equal to 1
in all number line and is, therefore, continue function in all points of the number line.