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Mathematics 10 Online
OpenStudy (anonymous):

Factor. 27^3-125

OpenStudy (mathstudent55):

Is that 27x^3 - 125?

OpenStudy (anonymous):

yeah, sorry

OpenStudy (mathstudent55):

There is a special factoring for this. Notice that the first term, 27x^3 is the cube of 3x. Also, 125 is 5^3. This is called a difference of cubes.

OpenStudy (anonymous):

Alright. Well, where would I go from there? I don't understand what to do :/

OpenStudy (mathstudent55):

a^3 - b^3 = (a - b)(a^2 + ab + b^2)

OpenStudy (mathstudent55):

That's the general rule for a difference of cubes. You have: (3x)^3 - 5^3, so for you, a = 3x, and b = 5, in the general rule.

OpenStudy (anonymous):

Oh, okay. Thanks! ^^ I think I've got it from here

OpenStudy (mathstudent55):

ok

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