Question 243995
Hello, 
I want to make sure you copied the problem correctly. The last number 540 in -3x3-21x2+72x+540 shouldn't it be 504? I'm going to assume it is 504. (Note: since it's an equation we'll set it to equal 0)
-3x3-21x2+72x+504=0 
First we do this: The first two terms can be rewritten as well as the last two.
-3x^2(x+7)+ 72(x+7)
Notice the (x+7) being the same so we can rewrite it as: 
(-3x^2+72)(x+7) the first parenthesis can be rewritten as:
-3(x^2-24)(x+7) Now we can solve for x:
x=-7
x=sq rt 24 or 2sq rt 6
Plug these into the original equation and it works out. 
RJ Toftness
www.math-unlock.com