rational expressions and equations

Question

2x-5/4x²-10x

 

Is the non premissible value equal to 0 and 5/2 or is it just 0?

 

 

Answer 1

Layne, you can't have 0 in your denominator.  The numerator doesn't matter.  0/5 = 0.  5/0 is undefined.  But, there's more to your answer than just 0, though it's not 5/2.

 

We set 5/4x²-10x = 0.

 

We can factor out x to get x(5/4x-10) = 0

 

Now, either part can equal 0.  We see that x = 0, like you said.

 

The second part, 5/4x-10, can also equal 0, so we set 5/4x-10 = 0.  5/4x = 10.  Now, we divide by 5/4.  Remember that in dividing fractions, we take the 2nd, flip it upside down, and multiply.

 

10 / (5/4) = 10 x 4/5 = 40/5 = 8.

 

So, our two answers are x = 0 and x = 8.

 

Hope this helps!