Question

What is the maximum or minimum value of the fiction y=2x^2+16x-4

Answer 1

First, try to picture the shape of the graph of y=2x^2+16x-4. Does this graph open up or open down?

If UP, then you've got a minimum somewhere (for some x-value); if DOWN, then you've got a max.

Before I go further, I need to ask whether you're in algebra or in calculus, as your course dictates which approach is the better in discussing the problem you've posted.