8. a cubic function with a leading coefficient of -2, with one positive zero.

Example:           - 2x³ + 10x²

Step-by-step explanation:

1.A cubic function is a polynomial of degree 3 in one variable. This means that the highest exponent of the variable is 3: x³

2. Leading coefficient is the coefficient of the term with the highest exponent: in ax³ the leading coefficient is a.

3. General form of a cubic function: ax³ + bx² + cx + d, where a ≠ 0

4. Zeros of a polynomial function are the values of x for which the polynomial values zero: ax³ + bx² + cx + d = 0

5. When the polinomial is factored you can tell easily which the zeros are.

This is how a factored cubic function looks: a(x - x₁)(x - x₂)(x - x₃), where a is the leading coefficient, and x₁, x₂, and x₃ are the three zeroes of the function.

With that, you can write a cubic function with the restrictions stated:

         result: f(x) = - 2( x -5)(x - 0)(x -0) = -2(x - 5)(x)(x)

         - 2x³ + 10x²