Find All Values of a for Continuous Function f on Real Numbers

[margbelladot]

How do you find all the values of "a" such that f is continuous on all real numbers?

Find all values of a such that f is continuous on $\Re$

f(x)= x+1 if x$\leq$ a
x^2 if x>a


I tried solving but i do not even know where to start! Please help!

 

[scurty]

We know (or you should know!) that x+1 and x^2 are continuous functions because they are polynomials. When you create a continuous piece-wise function, $f(x)$, you want $f(a)$ to be continuous. This means $\displaystyle \lim_{x \to a^-} f(a) = \lim_{x \to a^+} f(a) = f(a)$

You can think of it in lay man's terms as choosing values of a so that you can graph the function without lifting your pencil at $f(a)$.