For what value of x is the function ƒ below undefinded?

Question

The function:

 

ƒ(x) = (x² - 10x + 25) / (2x² - 24x + 72)

 

Please help. I tried and got 5/6, but it is wrong. Thank you!

Answer 1

Hi Anna,

 

To determine where the function is undefined, you'll need to identify which x value makes the denominator and only the denominator equal to 0.

 

If you factor the numerator and the denominator into binomials, you'll be able to determine the x value that makes the denominator binomials equal to 0. If the numerator binomials also equal 0 with the same x value, then that x value does not make the function undefined. The numerator has to be a number other than 0 while the denominator has to be 0.

 

Let me know if you have any other questions.  

Answer 2

Set the equation equal to 0

 

2x^2 - 24X + 72 = x^2 - 10x +25

 

x^2 -24x + 72 = -10x +25

 

x^2 - 14x + 72 = 25

 

X^2 -14x + 47 = 0

 

Use the quadratic formula

 

14 +/- squareroot 14^2 - 4 (1) (47) (divided by) 2

 

after calculation, my answer is 7 +/- squareroot of 2