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# Domain

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What is the sum of all values of y for which the expression (y + 6)/(y^2 - 4y + 4) is undefined?

May 5, 2022

#1
+2440
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For the equation to be undefined, the denominator must equal 0, because anything divided by 0 is undefined.

Thus, we have the equation: $$y^2-4y+4=0$$, where we have to solve for y.

To solve for y, use the quadratic formula: $$y = {-b \pm \sqrt{b^2-4ac} \over 2a}$$ , because the quadratic is in the form $$ax^2+bx+c=0$$

Can you do it from here?

May 5, 2022
#2
+124595
+1

y^2 - 4y + 4  factors as    (y -2)^2

So

(y -2)^2 = 0

So  when y = 2, the denominator   = 0  and  the expression is undefined

May 5, 2022