# Odd factoring in textbook

• Oct 25th 2009, 04:43 PM
hibernaldream
Odd factoring in textbook
Though this is for a calculus problem, I've gotten all the calc worked out. I just don't understand how the book came to this conclusion after factoring!

$3x^2 - 12x + 11 = 0$
The answer the book comes to is

$(6 + sqrt(3)) / 3$
$(6 - sqrt(3)) / 3$

The way I did it in the first place was:
$3x^2 - 12x = -11$
$3x(x - 4) = -11$
Therefore
$x = -11 / 3$
$x = -7$

What were they doing in my textbook? Unfortunately they give no clues and I've been staring at it for 15 minutes now.
• Oct 25th 2009, 04:53 PM
skeeter
Quote:

Originally Posted by hibernaldream
Though this is for a calculus problem, I've gotten all the calc worked out. I just don't understand how the book came to this conclusion after factoring!

$3x^2 - 12x + 11 = 0$
The answer the book comes to is

$(6 + sqrt(3)) / 3$
$(6 - sqrt(3)) / 3$

The way I did it in the first place was: this is not the correct method to solve a quadratic equation.
$3x^2 - 12x = -11$
$3x(x - 4) = -11$
Therefore
$x = -11 / 3$
$x = -7$

What were they doing in my textbook?