# Functions.Determine whether f(x) = 3x^4 - 5x^2 + 2 is even odd or neither.

justaguide | College Teacher | (Level 2) Distinguished Educator

Posted on

A function is even if f(-x) = f(x) and it is odd if f(-x) = -f(x)

f(x) = 3x^4 - 5x^2 + 2

f(-x) = 3*(-x)^4 - 5*(-x)^2 + 2

=> 3*x^4 - 5x^2 + 2

=> f(x)

This shows that f(x) = 3x^4 - 5x^2 + 2 is even.

giorgiana1976 | College Teacher | (Level 3) Valedictorian

Posted on

A function is even if

f(-x) = f(x)

In other words, plugging in a number will be the same as plugging in the negative value of the same number.

We'll analyze the given function, replacing each x by -x.

f(-x) = 3(-x)^4 - 5(-x)^2 + 2

We'll compute raising -x to the 4th and 2nd powers and we'll get:

(-x)^4 = (-x)(-x)(-x)(-x) = x^2*x^2 = x^4

f(-x) = 3(x)^4 - 5(x)^2 + 2

So we can see that:

f(-x) = f(x) which means that the function f(x) is an even function.

An even function has symmetry across the y-axis. We also know that if all of the exponents are even, then the function is even.