If a function is continuous at 0, find the values of two constants a and b !enter image description here What approach should I take? I am practising for my Calc Final and I've some problems trying to understand these kind of examples.

You should basically know that if a function $f$ is continuous at $x=a$ then,

$$f(a)=\lim_{x\rightarrow a^+}f(x)=\lim_{x\rightarrow a^-}f(x)=\lim_{x\rightarrow a}f(x)$$