The evaluation of this expression is in the proper reading of the notation:
–x^2 + 2x – 4
is the same as:
= –(x)^2 + 2(x) – 4
the parentheses are implicit, but inform the evaluator. This is then rewritten more clearly as:
= –(x * x) + 2(x) – 4
which then evaluates under x = 5 by:
= –(5 * 5) + 2 * 5 – 4
where " * " is multiplication. The rest is computation is straightforward, with proper use of order of operations.