# Math Help - Finish this equation

1. ## Finish this equation

$3(x-3)^3=375$
$(x-3)^3=125$
$x^3-9x^2+27x-9=125$
$x^3-9x^2+27x-134=0$

Not sure where to go from here

2. ## Re: Finish this equation

y3 = 125 is equivalent to y = 5.

3. ## Re: Finish this equation

Sorry? What y? I need to find the value of x. The answer is supposedly 8.

4. ## Re: Finish this equation

Originally Posted by helvenmarn
Sorry? What y? I need to find the value of x. The answer is supposedly 8.
$(8-3)^3=125$

5. ## Re: Finish this equation

$(x-3)^3=125$
Since $125=5^3$ then $(x-3)^3=5^3$.
From this we have that x-3=5 or x=8

Ah thanks

7. ## Re: Finish this equation

No need to expand.

From $(x-3)^3 = 125$, we get $x-3 = 5 \Rightarrow x = 8$. There are also two roots in the complex plane, $x = 3 + 5e^{\frac{2\pi i}{3}}$ and $x = 3 + 5e^{\frac{4\pi i}{3}}$