Show that the equation has exactly one real root. x5 + ex = 0 Let f(x) = x5 + eX. Then (-1) = 0 and (o) = 0. Since f is the sum of a polynomial and the natural exponential function, f is continuous and differentiable for all x. By the Intermediate Value Theorem, there is a number c in (-1,0) such that f(c) = 0. Thus, the given equation has at least one real root. If the equation has distinct real roots a and b with a < b, then f(a) = f(b) = 0. Since f is continuous on [a, b] and differentiable on (a, b), Rolle's Theorem implies that there is a number r in (a, b) such that fr) = 0. But f'(r) = 0. This contradiction shows that the given equation can't have two distinct real roots, so it has exactly one root.

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Chapter1: Functions And Models
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Show that the equation has exactly one real root.
x5 + ex = 0
Let f(x) = x5 + eX. Then (-1) =
0 and (o) =
0. Since f is
the sum of a polynomial and the natural exponential function, f is continuous
and differentiable for all x. By the Intermediate Value Theorem, there is a
number c in (-1,0) such that f(c) = 0. Thus, the given equation has at least
one real root. If the equation has distinct real roots a and b with a < b, then
f(a) = f(b) = 0. Since f is continuous on [a, b] and differentiable on (a, b), Rolle's
Theorem implies that there is a number r in (a, b) such that fr) = 0. But
f'(r) =
0. This contradiction shows that the given equation can't
have two distinct real roots, so it has exactly one root.
Transcribed Image Text:Show that the equation has exactly one real root. x5 + ex = 0 Let f(x) = x5 + eX. Then (-1) = 0 and (o) = 0. Since f is the sum of a polynomial and the natural exponential function, f is continuous and differentiable for all x. By the Intermediate Value Theorem, there is a number c in (-1,0) such that f(c) = 0. Thus, the given equation has at least one real root. If the equation has distinct real roots a and b with a < b, then f(a) = f(b) = 0. Since f is continuous on [a, b] and differentiable on (a, b), Rolle's Theorem implies that there is a number r in (a, b) such that fr) = 0. But f'(r) = 0. This contradiction shows that the given equation can't have two distinct real roots, so it has exactly one root.
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