SOLUTION: Which numbers cannot be used in place of the variable in each rational expression? 18. 2y + 1 y2 � y -6

Question 168684: Which numbers cannot be used in place of the variable in each rational expression?
18. 2y + 1
y2 � y -6

Answer by jim_thompson5910(35256) (Show Source): You can put this solution on YOUR website!

Start with the given expression

Set the denominator equal to zero. Remember, dividing by 0 is undefined. So if we find values of y that make the denominator zero, then they cannot be used in place of the variable

Factor the left side (note: if you need help with factoring, check out this solver)

Now set each factor equal to zero:

or

or Now solve for y in each case

So our solutions are or

Since and make the denominator equal to zero, this means these values CANNOT be used in the rational expression

So and cannot be used.
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