1. ## Algebra Question

1-Find all numbers that, Rational Expression is not defined;
(Hint, Factor Denominator))
_2X – 10__
X2 - 8X + 15

a.
The Numbers are: X = - 5 and X = - 3

b.
The Numbers are: X = 5 and X = 3

c.
The Numbers are: X = 5 and X = - 3

d.
The Numbers are: X = - 5 and X = 3

2. Originally Posted by rdfisch
1-Find all numbers that, Rational Expression is not defined;
(Hint, Factor Denominator))
_2X – 10__
X2 - 8X + 15

a.
The Numbers are: X = - 5 and X = - 3

b.
The Numbers are: X = 5 and X = 3

c.
The Numbers are: X = 5 and X = - 3

d.
The Numbers are: X = - 5 and X = 3
Hello rdfisch,

Before we get started on this question. It doesn't belong in The Advanced algebra section.(alot of folks wont look here). Try using Algebra or urgent help for a faster responce.

Since we are not allowed to divide by zero, we want to find all values of x that would make the denominator zero.

$x^2-8x+15=0$ since the b term (the middle one) is negative and the c term (the constant) is positive both factors must be negative.

so we need factors of 15 that add up to -8

the factors of 15 are 1,15 and 3,5

since 3+5=8 this is what we want so we get...

$x^2-8x+15=0 \iff (x-3)(x-5)=0$

setting each factor equal to zero and solving we get x=3 and x=5

I hope this helps.

The answer is where x=5 and x=3, so b.

because x^2 - 8x + 15 = (x-5)(x-3)

Any numbers that make the denominator 0 makes the expression not defined.

Originally Posted by rdfisch
1-Find all numbers that, Rational Expression is not defined;
(Hint, Factor Denominator))
_2X – 10__
X2 - 8X + 15