Question

Given f(x) = −15x − 2x2 + x3, is there a zero of f(x) between a = 4 and b = 6?

Answer 1

looks like there is because
f(4) is negative and f(6) is positive

Answer 2

lets try factoring this - x is the gcf:
= x(x^2 - 2x - 15)
= x (x - 5)(x + 3)
right - that confirms your query -
one zero is between 4 and 6 (that is 5 )and the other two are 0 and -3