Question

What is the vertex of the graph of y = –x2?
(–1, 0)
(0, –1)
(0, 0)
(1, 1)

Answer 1

consider y = x^2 first (we'll address the negative sign later)

notice how for positive integers, x^2 keeps increasing as x increases
for negative integers, x^2 also keeps increasing as x decreases

but for x = 0, y = 0. this is the minimum value. (x^2 cannot be less than 0). therefore, we conclude that y = x^2 has a vertex at (0,0)

now, multiplying the function by -1 does not change the vertex, simply the direction of the graph.