Let
f(x)={x2−4,ax+b,x≤1,x>1,
where a and b are real constants.
a. Determine all ordered pairs (a,b) for which f is continuous on the closed interval [−2,3].
b. For each pair (a,b) you found in part (a), justify that there exists at least one number c in [−2,3] satisfying f(c)=0.