Chapter 5 Polynomials and Polynomial Functions - 5.9 Write Polynomial Functions and Models - 5.9 Exercises - Quiz for Lessons 5.7-5.9 - Page 399: 11

$f(x)=-0.5(x+5)(x+2)(x-2)$.

If the function has x-intercepts $a,b,c$, then it has the form $f(x)=k(x-a)(x-b)(x-c)$. Here the x-intercepts are $-5,-2,2$, hence $f(x)=k(x+5)(x+2)(x-2)$. The function also goes through $(1,9)$, hence: $9=k(6)(3)(-1)=-18k\\k=-0.5$