A few days ago
Anonymous

Absolute value expressions as piecewise expressions?

Write the following absolute value expressions as piecewise expressions:

|x^2-1|

|x^2+x-12|

|x^2+4x+4|

(If you can show me how to do one, I’ll figure out the other 2!)

Top 2 Answers
A few days ago
hayharbr

Favorite Answer

First find where each one equals zero. That defines the starting points for each piece. Example:

x^2 + x – 12 = (x + 4)(x – 3) and equals zero if x = -4 or 3

So the pieces are: x < -4, -4 < x < 3, and x > 3 [with two of the inequalities including = so -4 and 3 aren’t left out]

Now, if x , -4, both parts are negative so the product is positive and the absolute value bars make no difference. Similarly if x > 3 both are positive and again they don’t change it. But in between (x-3) is negative while (x + 4) is positive so the absolute value changes its sign.

Answer: (with the big curly brace)

x^2 + x – 12 if x >= 3 or x <= -4 -(x^2 + x - 12) if -4 < x < 3

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5 years ago
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See where they equal zero, then do the positive value to the right of there and the negative value to the left. Like the first one equals zero if x = 2 so y = 2x – 4, x ≥ 2 y = – (2x – 4) [or -2x + 4] , x < 2
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