Question

Which of the following is an even function?

f(x) = |X|
f(x) = x - 1
f(x) = -3%
F(x) = 2x

Answer 1

It's the first one.

Explanation:

One test to see if a function is even is to check f(x) and f(-x). If they are equal then the function is even.

f(x) = |x| :

If x = x then f(x) = x, if x = -x then f(-x) = x, so this is an even function.

Answer 2

f(x) = |x|

Explanation:

f(x) = x - 1 is a linear graph (remember y=mx+b)

So this line has a slope of 1, but just starts at y=-1

The f(x) = 2x is also linear

f(x) = |x| is a straight line, but one that never crosses below the x axis, because x is always a positive number (hence the |absolute| brackets). Therefor it makes a kind of upside down pyramid shaped graph that is a function.