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anonymous
 4 years ago
Ok guys...this college algebra stuff is kicking my butt! Here is the problem. I'll show it step by step of how my book has it:
1) 27t^3  64 =0
2) (3x)^3  (4) ^3
3) (3x4) (9x + 12x + 16) = 0
After that, the solve for the 3x4, and the 9x+12x+16 (the latter is a quadratic equation using the quadratic formula). I totally understand how to work both of those, however what I'm stuck on is how they get from step 2 to step 3... I have a feeling once someone says it, I'm going to be like "duh" Can someone help me get to the "duh" point??
anonymous
 4 years ago
Ok guys...this college algebra stuff is kicking my butt! Here is the problem. I'll show it step by step of how my book has it: 1) 27t^3  64 =0 2) (3x)^3  (4) ^3 3) (3x4) (9x + 12x + 16) = 0 After that, the solve for the 3x4, and the 9x+12x+16 (the latter is a quadratic equation using the quadratic formula). I totally understand how to work both of those, however what I'm stuck on is how they get from step 2 to step 3... I have a feeling once someone says it, I'm going to be like "duh" Can someone help me get to the "duh" point??

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anonymous
 4 years ago
Best ResponseYou've already chosen the best response.01st one is a difference of 2 cubes

anonymous
 4 years ago
Best ResponseYou've already chosen the best response.0You want to know how to use the quadratic formula?

anonymous
 4 years ago
Best ResponseYou've already chosen the best response.0No, I know how to use the quadratic formula. That's the easy part for me. I guess what I don't understand is finind the difference between the two squares

anonymous
 4 years ago
Best ResponseYou've already chosen the best response.0No wait, I know how to find the difference. What I'm struggling on is how they get from step 2 to step 3. What is the process?

anonymous
 4 years ago
Best ResponseYou've already chosen the best response.0\[\frac{b \pm \sqrt{b^24ac}}{2a}\]

anonymous
 4 years ago
Best ResponseYou've already chosen the best response.0What step exactly do you mean?

anonymous
 4 years ago
Best ResponseYou've already chosen the best response.0How do they get this: (3x)^3  (4) ^3 3) to this: (3x4) (9x + 12x + 16) =

anonymous
 4 years ago
Best ResponseYou've already chosen the best response.0Formula used is a^3  b^3 = (ab)(a^2 + a*b + b^2)

anonymous
 4 years ago
Best ResponseYou've already chosen the best response.0Yes that is the difference of 2 cubes

cristiann
 4 years ago
Best ResponseYou've already chosen the best response.0You use the formula a^3b^3=(ab)(a^2+ab+b^2) which you may easily verify by multiplying in the righthand term

anonymous
 4 years ago
Best ResponseYou've already chosen the best response.0Ok, I understand it is the difference of two cubes, what I don't understand is how they do it. Is it distributing?

anonymous
 4 years ago
Best ResponseYou've already chosen the best response.0It's just a special rule

anonymous
 4 years ago
Best ResponseYou've already chosen the best response.0Ok, having the formula is helping now

anonymous
 4 years ago
Best ResponseYou've already chosen the best response.0The sum of 2 cubes would be: \[a^3+b^3=(a+b)(a^2ab+b^2)\]

radar
 4 years ago
Best ResponseYou've already chosen the best response.1The rule is\[x ^{3}a ^{3}=(xa)(x ^{2}+ax+a ^{2})\]

anonymous
 4 years ago
Best ResponseYou've already chosen the best response.0thank you!!! my book doesn't say anything about using the formula. That's exactly what I was stuck on.

radar
 4 years ago
Best ResponseYou've already chosen the best response.1You have to memorize it or just remember that there is factors of the difference of two perfect cubes.

radar
 4 years ago
Best ResponseYou've already chosen the best response.1There is also one for the sum of two perfect cubes. In this case it is the difference you are working with.

anonymous
 4 years ago
Best ResponseYou've already chosen the best response.0Yes, I threw that in above in case you need it in the future

radar
 4 years ago
Best ResponseYou've already chosen the best response.1Which I believe it will be needed.

anonymous
 4 years ago
Best ResponseYou've already chosen the best response.0thank you, I wrote down both of them. Thanks guys!!
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