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1. Multiply by the conjugate
2. You can factor t^3-64 (a=t and b=-4) by following the identity a^3+b^3=(a+b)(a^2-ab+b^2)
3. Cancel the common terms (t-4)
4. You should have 3(sqrt(t)+2)(t^2 + 4t + 16)
5 Solve.. ans should be 576

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could anyone refresh me on conjugates?

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the conjugate is like the "partner" expression. in ths case it is being use to cancel out the sqrt from the denominator.
basically you multiply the expression (a+b) by its opposite (a-b)
in this case, (sqrt(t)-2)is multiplied by (sqrt(t)+2).
which gives the difference between two squares

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Awesome, thanks Todd.