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C3 help!!!!

for graphing y=f(IxI)
why is it a reflection in the y axis, i thought the makes all X values positive and that means Y values too????

Reply 1

Matrix123

Original post by JustgotAstar

for graphing y=f(IxI)
why is it a reflection in the y axis, i thought the makes all X values positive and that means Y values too????

The y value of the negative x values becomes positive. By drawing this part of the graph with the positive parts, it looks like it's a reflection in the y axis.
It's just a linear function that meets the x axis at y=0 so the reflection is in y=0, the y axis.

Spoiler

(edited 6 years ago)

Reply 2

Faction Paradox

If you take f(x) = x that will mean y = |x|
So the y value when x = -2 will be the same as when x = 2 so it is going to be reflected in the y axis

However if f(x) = x-4 that will mean y = |x|-4 so values where |x|<4 the y value will be negative, so it doesn't always follow that y = f(|x|) produces positive values of y, it depends of the function f(x)

Reply 3

Tierniesta

The X value can be a negative, however the modulus of a plus or minus value is always positive i.e so when X = -3, Y = 3 as the -3 is converted into a 3, so the Y value never goes below 0.

Reply 4

BrasenoseAdm

Official Rep

Original post by JustgotAstar

for graphing y=f(IxI)
why is it a reflection in the y axis, i thought the makes all X values positive and that means Y values too????

Try plotting the simplest function: y = x and then plot y = modulus x. See what happens!

Reply 5

y.u.mad.bro?

The value of y will be positive regardless of |x| being positive or negative because the modulus function states that the value will be positive hence the positive y values. I just remember it like this because it makes it easier to understand and apply unless you are doing complicated problems.