Which equation represents a graph with a vertex at open paren 1 comma negative 6 close paren ?

For a quadratic equation y = ax² + bx + c, the vertex’s x-coordinate is −b/(2a). In choice D, that is −(−6)/(2·3) = 1; substituting x = 1 gives y = 3 − 6 − 3 = −6, so the vertex is (1, −6).

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