Linear or Not?

Question

Determine whether the following function is linear 

 

y = x^3 - 3x

 

Explain why

 

 

 

Answer 1

Whenever you have a polynomial (check the definition), it's linear if it's of degree 1; the general form of a line (linear function) is y = mx + b.  This function doesn't qualify, because it's cubic, i.e. degree 3.  This should be obvious.