Rogelio is asked to sketch a graph of g(x)=3x^3(x-5)^2(5-x)^4. How many turning points should his sketch include?

1 answer

To determine how many turning points the function \( g(x) = 3x^3(x-5)^2(5-x)^4 \) has, we need to analyze its derivatives and critical points.

The function is a polynomial, so we can find its turning points by looking at its first derivative \( g'(x) \).

  1. Finding the degree of the polynomial:

    • The polynomial \( g(x) \) can be expressed as: \[ g(x) = 3x^3 \cdot (x-5)^2 \cdot (5-x)^4 \]
    • The degree of \( g(x) \) is the sum of the degrees of its factors:
      • The degree of \( 3x^3 \) is 3.
      • The degree of \( (x-5)^2 \) is 2.
      • The degree of \( (5-x)^4 \) is 4.
    • Therefore, the total degree of \( g(x) \) is \( 3 + 2 + 4 = 9 \).
  2. Finding the number of turning points:

    • The maximum number of turning points of a polynomial of degree \( n \) is \( n - 1 \).
    • In this case, since the degree of \( g(x) \) is 9, the maximum number of turning points is \( 9 - 1 = 8 \).
  3. Counting the actual turning points:

    • However, we also need to consider the multiplicity of the roots:
      • The root \( x = 0 \) has a multiplicity of 3.
      • The root \( x = 5 \) has a multiplicity of 2.
      • The root \( x = 5 \) (from the factor \( (5-x)^4 \)) is also related, as it will affect the symmetry and where the derivatives change signs.
    • The behavior of the function near these roots and their multiplicity affects whether they contribute to turning points.

Since \( x = 0 \) (multiplicity 3, not a turning point), \( x = 5 \) (multiplicity 2, contributes turning point), and \( x = 5 \) from \( (5-x)^4 \) (this root contributes a local maximum behavior).

Thus, \( g(x) \) will have \( 8 \) turning points in total but checking for multiplicity where the roots are located effectively will narrow down actual contributing turning points.

Conclusion:

The maximum possible number of turning points for the function \( g(x) = 3x^3(x-5)^2(5-x)^4 \) is 8, although there may be fewer actual turning points depending on the nature of the roots and multiplicity.