NAME
4-3
DATE
PERIOD
Word Problem Practice
Solving Quadratic Equations by Factoring
1. FLASHLIGHTS When Dora shines her
flashlight on the wall at a certain angle,
the edge of the lit area is in the shape of
a parabola. The equation of the parabola
is y = 2x2 + 2x - 60. Factor this
quadratic equation.
4. PROGRAMMING Ray is a computer
programmer. He needs to find the
quadratic function of this graph for an
algorithm related to a game involving
dice. Provide such a function.
y
2(x - 5)(x + 6)
4
2
O
2
4
6
8
10
12 x
-2
2. SIGNS David was looking through an
old algebra book and came across this
equation.
f (x) = x 2 - 18x + 77
6x + 8 = 0
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
The sign in front of the 6 was blotted
out. How does the missing sign depend
on the signs of the roots?
5. ANIMATION A computer graphics
animator would like to make a realistic
simulation of a tossed ball. The animator
wants the ball to follow the parabolic
trajectory represented by the quadratic
equation f(x) = -0.2(x + 5) (x - 5).
The missing sign is the opposite
of the sign of the two roots,
because their product is a
positive number, 8.
a. What are the solutions of f (x) = 0?
x = -5 or x = 5
3. ART The area in square inches of the
drawing Maisons prés de la mer by
Claude Monet is approximated by the
equation y = x2 – 23x + 130. Factor the
equation to find the two roots, which are
equal to the approximate length and
width of the drawing.
b. Write f (x) in standard form.
f (x) = -0.2x 2 + 5
c. If the animator changes the equation
to f(x) = -0.2x2 + 20, what are the
solutions of f(x) = 0?
10 inches by 13 inches
x = -10 or x = 10
Chapter 4
21
Glencoe Algebra 2
Lesson 4-3
x2
-4