Solving Equations Examples And Worksheet Page 7

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A55
Appendix A.5
Solving Equations
Example 8
The Quadratic Formula: Two Distinct Solutions
WARNING / CAUTION
2
When using the Quadratic
Use the Quadratic Formula to solve
x
3x
9.
Formula, remember that before
Solution
the formula can be applied, you
2
x
3x
9
must first write the quadratic
Write original equation.
equation in general form.
2
x
3x
9
0
Write in general form.
±
2
b
b
4ac
x
Quadratic Formula
2a
±
2
3
3
4
1
9
Substitute
a
1,
x
b
3,
and c
9.
2
1
±
3
45
x
Simplify.
2
±
3
3 5
x
Simplify.
2
The equation has two solutions:
3
3 5
3
3 5
x
and
x
.
2
2
Check these in the original equation.
Now try Exercise 87.
Example 9
The Quadratic Formula: One Solution
2
Use the Quadratic Formula to solve
8x
24x
18
0.
Solution
2
8x
24x
18
0
Write original equation.
Divide out common
2
4x
12x
9
0
factor of 2.
±
2
b
b
4ac
x
Quadratic Formula
2a
±
2
12
12
4
4 9
Substitute
a
4,
x
b
12,
and c
9.
2
4
±
12
0
3
x
Simplify.
8
2
3
This quadratic equation has only one solution:
x
.
Check this in the original
2
equation.
Now try Exercise 91.
Note that Example 9 could have been solved without first dividing out a common
factor of 2. Substituting
a
8,
b
24,
and
c
18
into the Quadratic Formula
produces the same result.

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