Question

What does the | symbol mean?

Example:

If f(x) = │x│ + 4, find f(−9).
Checking the answer:
f(−9) = │−9│ + 4
f(−9) = 9 + 4
f(−9) = 13

Does it mean do the opposite? -9 was changed to 9.. /:

Answer 1

absolute value
so make the 9 +

Answer 2

|-9| = 9

Answer 3

f(-9) = |-9| + 4
= 9 + 4
= 13

Answer 4

So it does mean to make a positive a negative or a negative a positive?

Answer 5

In any case?

Answer 6

you can take anyone first... it may be either a positive first or a negative... and V.V...

Answer 7

just makes whatever is inside the || lines positive

Answer 8

And if it is originally a positive, it will stay a positive?

Answer 9

|x| = sqrt ( x^2 ) you could rewrite it as the square root of the square

Answer 10

Or does that ever happen?

Answer 11

and yes...

Answer 12

If it is originally positive, it stays positive
if it was negative, the absolute value function returns a positive

Answer 13

so whatever goes in comes out positive

Answer 14

\(\LARGE x =\begin{cases} |x| = x & x > 0\\ |x| = 0& x = 0 \\ |x| = -x & x < 0\end{cases} \)

Answer 15

Thank you all so much!