C. The property seen in the graph is symmetry on the y-axis
D. The even function is defined by f(x) = f(-x)
How to show that the function is an even function
An even function is a function f(x) that satisfies the property
This means that if you replace x with -x in the function, you get the same output
Check
P(x) = x⁴ - 8x² + 16
P(-x) = (-x)⁴ - 8(-x)² + 16
P(-x) = x⁴ - 8x² + 16
Comparing with the original function shows that P(-x) = P(x). Hence the function is even.