Precalculus · Problem 3.1.37

Polynomial Functions — Stitz & Zeager

Mathematics — Precalculus · polynomial-zeros-multiplicity-graph

Problem

There is one subtlety about the role of multiplicity that we need to discuss further; specifically we need to see 'how' the graph crosses the xx-axis at a zero of odd multiplicity. In the section, we deliberately excluded the function f(x)=xf(x) = x from the discussion of the end behavior of f(x)=xnf(x) = x^n for odd numbers nn and we said at the time that it was due to the fact that f(x)=xf(x) = x didn't fit the pattern we were trying to establish. You just showed in the previous exercise that the end behavior of a linear function behaves like every other polynomial of odd degree, so what doesn't f(x)=xf(x) = x do that g(x)=x3g(x) = x^3 does? It's the 'flattening' for values of xx near zero. It is this local behavior that will distinguish between a zero of multiplicity 1 and one of higher odd multiplicity. Look again closely at the graphs of a(x)=x(x+2)2a(x) = x(x+2)^2 and F(x)=x3(x+2)2F(x) = x^3(x+2)^2 from Exercise 3.1.1. Discuss with your classmates how the graphs are fundamentally different at the origin. It might help to use a graphing calculator to zoom in on the origin to see the different crossing behavior. Also compare the behavior of a(x)=x(x+2)2a(x) = x(x+2)^2 to that of g(x)=x(x+2)3g(x) = x(x+2)^3 near the point (−2,0)(-2, 0). What do you predict will happen at the zeros of f(x)=(x−1)(x−2)2(x−3)3(x−4)4(x−5)5f(x) = (x-1)(x-2)^2(x-3)^3(x-4)^4(x-5)^5?

Browse the problem library