Complex Numbers - Cool math Algebra Help Lessons

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Coolmath Algebra
Complex Numbers Lesson 3 - The Quadratic Formula (page 1 of 2)
---- This algebra lesson explains how to use the quadratic formula when you get complex solutions.

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There is one main place that complex numbers will pop up on you:

The Quadratic Formula!

Sometimes, you'll get negative numbers under that radical.

Here's an example:

Solve

x = 6 +/- sqrt( 36 - 4 ( 25 ) ) / 2 = 6 +/- sqrt( -64 ) / 2 = 6 +/- 8i / 2 ... which you can rewrite as 6/2 +/- 8i/2 = 3 +/- 4i

So, the solutions are

Here's another one:

Solve

x = -1 +/- sqrt( 1 - 4 ( 2 ) ( 25 ) ) / 4 = -1 +/- sqrt( -79 ) / 4 = -1 +/- sqrt( 79 ) i / 4

{ ( -1 - sqrt( 79 ) i ) / 4 , ( -1 + sqrt( 79 ) i ) / 4 }

YOUR TURN:

Solve

Continued on the next page

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