Question

If possible, choose k so that the following function is continuous on any interval:

Answer 1

We need to cancel out the discontinuity in x = 4

In order to do that, factorize the numerator:
5x⁴ - 20x³ = 5x³(x-4)

This way, your function will be:
f(x) = 5x³(x-4) / (x-4)

and the two parentheses cancel out, leaving
f(x) = 5x³ 

which at x = 4 gives:
f(4) = 5·4³ = 5 · 64 = 320

Therefore K = 320.