Suppose is continuous at but does not exist

MATHEMATICS · Subjective · A Level · Mathematics · Differentiation · Differentiation

Problem

Suppose

f

is continuous at

x=5

but

f'(5)

does not exist, while

f

is discontinuous at

x=7

. In one sentence, indicate which of the points

x=5

and

x=7

could be a location of a relative extremum of

f

and justify your choice.