Step-by-step explanation:
y = -2x² + 4x + 1
Complete the square.
y = -2 (x² − 2x) + 1
y = -2 (x² − 2x + 1) + 1 − (-2)(1)
y = -2 (x − 1)² + 3
The vertex is (1, 3). The leading coefficient is negative, so the vertex is a maximum.
Graph: desmos.com/calculator/qsih3rd8ev