Find the domain of the rational expression: 8-x/7x+21

Question

im lost on this. no idea how to do these.

Answer 1

Set the denominator term equal to zero and solve for x.

 

The domain is all real numbers except for the x value you solved for, because that x value is the restricted value.

Answer 2

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Answer 3

I am going to assume you left off the grouping parenthesis

...VERY Important to include grouping parenthesis....

and this should be:

 

(8-x)/(7x+21)

 

The domain is the set of all possible input values x.

The only restriction on x in this expression is that,

since we cannot divide by zero, 7x+21 ≠ 0

 

7x+21=0

7x = -21

x = -3

 

x can be any number except -3

 

Domain in interval notation is  (-∞,-3)U(-3,∞)

 

In set notation   Domain = {x:  x∈R, x≠-3}