SOLUTION: 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 =

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons  -> Quadratic Equation Lesson -> SOLUTION: 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 =      Log On


   

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

Answer by Edwin McCravy(20054) About Me  (Show Source):
You can put this solution on YOUR website!

You don't have the formula right:

The solution to

ax%5E2%2Bbx%2Bc=0

is

x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+


Your problem is 

9x%5E2+-+12x+-+4+=+0

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

x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+



x+=+%2812+%2B-+sqrt%28144%2B144%29%29%2F%282%2A%289%29%29+
 
x+=+%2812+%2B-+sqrt%28288%29%29%2F18+

x+=+%2812+%2B-+sqrt%28144%2A2%29%29%2F18+

x+=+%2812+%2B-+sqrt%28144%29sqrt%282%29%29%2F18+

x+=+%2812+%2B-+12sqrt%282%29%29%2F18+

Factor 12 out of the top

x+=+12%281+%2B-+sqrt%282%29%29%2F18+

Divide 12 and 18 by 6

x+=+2%281+%2B-+sqrt%282%29%29%2F3+

That is equivalent to your answers:

Edwin