#### wwdawg

##### New member
"For what value of m is the following rational equation undefined"
m - 8/m = - 4

the answer must be an equation. What even? I'm so confused!

#### Dr.Peterson

##### Elite Member
"For what value of m is the following rational equation undefined"
m - 8/m = - 4

the answer must be an equation. What even? I'm so confused!
The answer will have the form "m = something".

Suppose I gave you a value for m, and you tried evaluating your expression. In what one case would you say, "I can't do it"? That will be the number they are asking for.

What number can't you divide by?

#### lev888

##### Senior Member
"For what value of m is the following rational equation undefined"
m - 8/m = - 4

the answer must be an equation. What even? I'm so confused!
Typo? Should be (m-8)/(m-4)? But then this is an expression, not an equation. And the answer is a value, not an equation either.

#### Subhotosh Khan

##### Super Moderator
Staff member
"For what value of m is the following rational equation undefined"
m - 8/m = - 4

the answer must be an equation. What even? I'm so confused!
Is the given rational equation:

$$\displaystyle m - \frac{8}{m} \ = -4$$

or

$$\displaystyle \frac{m - 8}{m} \ = -4$$

#### HallsofIvy

##### Elite Member
If the equation is m- 8/m= -4 then clearly m cannot be 0. Multiplying both sides by m gives m^2- 8= -4m or
m^2+ 4m- 8= 0. That is a quadratic equation that can be solved by completing the square or using the quadratic formula.

If, as Subhotosh Kahn suggested, you meant (m- 8)/m= -4 (m- 8/m would be bad notation here but many people make that mistake) then multiplying both sides by m, m- 8= -4m which reduces to 5m= 8.

#### lev888

##### Senior Member
If the equation is m- 8/m= -4 then clearly m cannot be 0. Multiplying both sides by m gives m^2- 8= -4m or
m^2+ 4m- 8= 0. That is a quadratic equation that can be solved by completing the square or using the quadratic formula.

If, as Subhotosh Kahn suggested, you meant (m- 8)/m= -4 (m- 8/m would be bad notation here but many people make that mistake) then multiplying both sides by m, m- 8= -4m which reduces to 5m= 8.
I doubt this is supposed to be an equation. What does it mean "the following rational equation is undefined"? An equation either has solutions or it doesn't. I've never heard an equation characterized as defined or undefined.