15.11.2014 Views

Intermediate Algebra – Student Workbook – Second Edition 2013

Intermediate Algebra – Student Workbook – Second Edition 2013

Intermediate Algebra – Student Workbook – Second Edition 2013

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

Lesson 5b - Solving Quadratic Equations<br />

Mini-Lesson<br />

Work through the following to see how to deal with equations that can only be solved in the<br />

Complex Number System.<br />

Problem 11<br />

WORKED EXAMPLE <strong>–</strong> SOLVING QUADRATIC EQUATIONS WITH<br />

COMPLEX SOLUTIONS<br />

Solve 2x 2 + x + 1= 0 for x. Leave results in the form of a complex number, a+bi.<br />

First, graph the two equations as Y1 and Y2 in your calculator and view the number of times the<br />

graph crosses the x-axis. The graph below shows that the graph of y = 2x 2 + x + 1 does not cross<br />

the x-axis at all. This is an example of our Case 3 possibility and will result in no Real Number<br />

solutions but two unique Complex Number Solutions.<br />

To find the solutions, make sure the equation is in standard form (check).<br />

Identify the coefficients a = 2, b = 1, c = 1.<br />

Insert these into the quadratic formula and simplify as follows:<br />

2<br />

1<br />

1 4(2)(1) 1<br />

18<br />

1<br />

7<br />

x <br />

<br />

2(2)<br />

4 4<br />

Break this into two solutions and use the a+bi form to get<br />

x<br />

1<br />

1<br />

7<br />

<br />

4<br />

1<br />

<br />

4<br />

1 i<br />

<br />

4<br />

1<br />

<br />

4<br />

7<br />

4<br />

7<br />

4<br />

7<br />

4<br />

i<br />

and<br />

x<br />

2<br />

1<br />

7<br />

<br />

4<br />

1<br />

<br />

4<br />

1 i<br />

<br />

4<br />

1<br />

<br />

4<br />

7<br />

4<br />

7<br />

4<br />

7<br />

4<br />

i<br />

The final solutions are<br />

x<br />

1<br />

<br />

4<br />

7<br />

i,<br />

x<br />

4<br />

1<br />

<br />

4<br />

1 2<br />

<br />

7<br />

i<br />

4<br />

Remember that<br />

1 i so 7 i 7<br />

Scottsdale Community College Page 225 <strong>Intermediate</strong> <strong>Algebra</strong>

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!