# One more quadratic equation

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• April 15th 2009, 09:32 AM
tbradnc
One more quadratic equation
Ok, I'm on my last problem and stuck again. :(

16r^3-9r=0

There's not an example in my textbook (chapter 6.6) to use as a guide (we're using "Introdutory Algebra, 8th edition by Lial, Hornsby, amd McGinnis).

Any assistance or pointers to help would be appreciated.

Thanks,
Thomas
• April 15th 2009, 09:41 AM
e^(i*pi)
Quote:

Originally Posted by tbradnc
Ok, I'm on my last problem and stuck again. :(

16r^3-9r=0

There's not an example in my textbook (chapter 6.6) to use as a guide (we're using "Introdutory Algebra, 8th edition by Lial, Hornsby, amd McGinnis).

Any assistance or pointers to help would be appreciated.

Thanks,
Thomas

Take out a common factor of r to give

r(16r^2-9) = 0

This gives r = 0 as a factor. You can then solve the other part by using the difference of two squares:

$
a^2-b^2 = (a-b)(a+b)
$

In your case a = 4r and b = 3
• April 15th 2009, 09:55 AM
tbradnc
Of course... thanks. As soon as you pointed it out I could see it.

Hoping this will all come together for me at some point.