Select the x-coordinate of the vertex of the parabola defined by the function f(x) = -3x2 + 7x + 9.
For a parabola written in standard form, i.e. f(x)=ax2+bx+c, its vertex can be found by (-b/(2a),f(-b/(2a)).
So, for f(x)=-3x2+7x+9, we have a=-3, b=7 and c=9. Therefore, the x-coordinate of the vertex is at:
-b/(2a) = -7/(2*-3) = -7/-6 = 7/6.