Page 53 - Math Course 3 (Book 1)

Quadratic Equations: Graphing

Your Turn!
x y

0 2 Factoring

1 –1 Use factoring to determine how many times the
2
graph of f(x) = x + 2x – 15 intersects the x-axis.
2 –2 Identify each root.
3 –1
f(x) = x – 4x +2 A. 2 times; x = 3 and x = 5
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4 2 B. 2 times; x = 3 and x = –5
C. 2 times; x = –3 and x = 5
The x-intercepts of the graph are between 0 and 1 D. 2 times; x = –3 and x = –5
and between 3 and 4.

One root is between 0 and 1, and
Answer Answer
the other root is between 3 and 4.

Rational Roots

2
Real World Example Solve x – 2x – 5.
MODEL ROCKETS A. One root is between 0 and 1,
Shelly built a model rocket for and the other root is between 4 and 5.
her science project. The equation B. One root is between –1 and 0,
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y = –16t + 250t models the flight of the rocket, and the other root is between 3 and 4.
launched from ground level at a velocity of 250 C. One root is between –1 and –2,
feet per second, where y is the height of the and the other root is between 3 and 4.
rocket in feet after t seconds. For how many D. Ø
seconds was Shelly’s rocket in the air?

You need to find the solution of the equation
2
0 = –16t + 250t. Use a graphing calculator to
2
graph the related function y = –16t + 250t.
The x-intercept is between 15 and 16 seconds.

Answer

Answer between 15 and 16 seconds

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