The equation
represents the polynomial graphed.
How to determine the equation of a polynomial
In this problem we must determine the equation of a polynomial, whose factor form is now defined:
f(x) = a · Π (x - rₙ), for {1, 2, 3, ..., n - 1, n}
Where a is the lead coefficient and rₙ is the n-th root.
If we know that r₁ = - 4, r₂ = - 2, r₃ = 1, r₄ = 4 (Multiplicity 2), Intercept: 4, then the polynomial is:
f(x) = a · (x + 4) · (x + 2) · (x - 1) · (x + 4)²
And the lead coefficient is:
4 = a · (0 + 4) · (0 + 2) · (0 - 1) · (0 + 4)²
4 = a · 4 · 2 · (- 1) · 16
4 = - 128 · a

The polynomial is defined by
.