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Please find pages 382 and 411 attached below. 6-8
Roots and Zeros
Main Ideas
• Determine the
number and type
of roots for a
polynomial equation.
• Find the zeros of a
polynomial function.
GET READY for the Lesson
When doctors prescribe medication, they give patients
instructions as to how much to take and how often it should be
taken. The amount of medication in your body varies with time.
Suppose the equation M(t) = 0.514 + 3.5+3 – 100+2 + 350t models
the number of milligrams of a certain medication in the bloodstream
t hours after it has been taken. The doctor can use the roots of
this equation to determine how often the patient should take the
medication to maintain a certain concentration in the body.
Types of Roots You have already learned that a zero of a function f(x) is
any value c such that f(c) = 0. When the function is graphed, the real zeros
of the function are the x-intercepts of the graph.
KEY CONCEPT
Zeros, Factors, and
Roots
Let f(x) = 0, x” + … +,x + a, be a polynomial function. Then the following
statements are equivalent.
• c is a zero of the polynomial function f(x).
• x- cis a factor of the polynomial f(x).
• c is a root or solution of the polynomial equation f(x) = 0.
In addition, if c is a real number, then (c, 0) is an intercept of the graph of f(x).
(У
CU
The graph of f(x) = x4 – 5×2 + 4 is shown at the
right. The zeros of the function are —2, -1, 1, and
2. The factors of the polynomial are x + 2, x + 1,
x – 1, and x – 2. The solutions of the equation
f(x) = 0 are -2,-1,1, and 2. The x-intercepts of the
graph of f(x) are (-2, 0), (-1,0), (1, 0), and (2,0).
19
Study Tip
Look Back
For review of
complex numbers,
see Lesson 5-4.
When
you solve a polynomial equation with degree greater than zero, it
may have one or more real roots, or no real roots (the roots are imaginary
numbers). Since real numbers and imaginary numbers both belong to the
set of complex numbers, all polynomial equations with degree greater than
zero will have at least one root in the set of complex numbers. This is the
Fundamental Theorem of Algebra.
KEY CONCEPT
Fundamental Theorem of Algebra
Every polynomial equation with complex coordinates and degree greater than
zero has at least one root in the set of complex numbers.
7-2
Inverse Functions
and Relations
GET READY for the Lesson
Main Ideas
• Find the inverse of a
function or relation.
• Determine whether
two functions or
relations are inverses.
Most scientific formulas involve measurements given in SI
(International System) units. The SI units for speed are meters per
second. However, the United States uses customary measurements
such as miles per hour.
To convert x miles per hour to an approximate equivalent in meters
per second, you can evaluate the following.
x miles . 1600 meters 1 hour
f(x)
or f(x) = x
1 hour 1 mile 3600 seconds
New Vocabulary
inverse relation
inverse function
identity function
one-to-one
To convert x meters per second to an approximate equivalent in miles
per hour, you can evaluate the following.
x meters 3600 seconds 1 mile
8(x) =
or g(x) = 2x
1 second 1 hour 1600 meters
Notice that f(x) multiplies a number by 4 and divides it by 9. The
function g(x) does the inverse operation of f(x). It divides a number by
4 and multiplies it by 9. These functions are inverses.
Find Inverses Recall that a relation is a set of ordered pairs. The inverse
relation is the set of ordered pairs obtained by reversing the coordinates
of each ordered pair. The domain of a relation becomes the range of the
inverse, and the range of a relation becomes the domain of the inverse.
KEY CONCEPT
Inverse Relations
Words
Two relations are inverse relations if and only if whenever one
relation contains the element (a, b), the other relation contains
the element (b, a).
Examples Q = {(1, 2), (3, 4), (5, 6)} S = {(2, 1), (4, 3), (6,5)}
Q and S are inverse relations.
EXAMPLE
Find an Inverse Relation
GEOMETRY The ordered pairs of the relation {(2, 1), (5, 1), (2, –4)}
are the coordinates of the vertices of a right triangle. Find the
inverse of this relation and determine whether the resulting
ordered pairs are also the vertices of a right triangle.
To find the inverse of this relation, reverse the coordinates of the
ordered pairs.
(continued on the next page)
Lesson 7-2 Inverse Functions and Relations 391
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