Questions on Algebra: Quadratic Equation answered by real tutors!

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Question 152616This question is from textbook Applied Calculus for the Managerial, Life and Social Sciences
: Use the quadratic formula to solve the following equation:
9x^2 - 12x = 4
The answer I worked was:
9x^2 - 12x - 4 = 0
x = -12 +/- sqrt 12^2 - 4(9)(4) / 2 (9)
x = 0/18
x = 0
However, in the book, it shows the answer as:
2/3(1 - sqrt 2); 2/3(1 + sqrt 2)
Can you please explain how I get to this answer? What am I doing wrong?
Thank you sooo much for your help.
This question is from textbook Applied Calculus for the Managerial, Life and Social Sciences
: Use the quadratic formula to solve the following equation:
9x^2 - 12x = 4
The answer I worked was:
9x^2 - 12x - 4 = 0
x = -12 +/- sqrt 12^2 - 4(9)(4) / 2 (9)
x = 0/18
x = 0
However, in the book, it shows the answer as:
2/3(1 - sqrt 2); 2/3(1 + sqrt 2)
Can you please explain how I get to this answer? What am I doing wrong?
Thank you sooo much for your help.

Answer by Edwin McCravy(2043) About Me  (Show Source):
You can put this solution on YOUR website!

You don't have the formula right:

The solution to

ax^2+bx+c=0

is

x = (-b +- sqrt( b^2-4*a*c ))/(2*a) 


Your problem is 

9x^2 - 12x - 4 = 0

a=9, b=-12, c=-4

x = (-b +- sqrt( b^2-4*a*c ))/(2*a) 

x = (-(-12) +- sqrt((-12)^2-4*(9)*(-4)))/(2*(9)) 

x = (12 +- sqrt(144+144))/(2*(9)) 
 
x = (12 +- sqrt(288))/18 

x = (12 +- sqrt(144*2))/18 

x = (12 +- sqrt(144)sqrt(2))/18 

x = (12 +- 12sqrt(2))/18 

Factor 12 out of the top

x = 12(1 +- sqrt(2))/18 

Divide 12 and 18 by 6

x = 2(1 +- sqrt(2))/3 

That is equivalent to your answers:

Edwin