Answer:x = [tex]\frac{3}{2}[/tex]Step-by-step explanation:Given the graph intersects the y- axis at (0, - 18), then substitute the coordinates into the equation y = x² + bx + c- 18 = 0 + 0 + c ⇒ c = - 18In the same way substitute (6, 0) into the equation0 = 6² + 6b - 180 = 36 + 6b - 180 = 18 + 6b ( subtract 18 from both sides )- 18 = 6b ( divide both sides by 6 )- 3 = bHence equation isy = x² - 3x - 18Given the equation in standard form : y = ax² + bx + c : a ≠ 0Then the x- coordinate of the vertex is[tex]x_{vertex}[/tex] = - [tex]\frac{b}{2a}[/tex]y = x² - 3x - 18 is in standard formwith a = 1, b = - 3, c = - 18, hence[tex]x_{vertex}[/tex] = - [tex]\frac{-3}{2}[/tex] = [tex]\frac{3}{2}[/tex]The x- coordinate of the turning point is [tex]\frac{3}{2}[/tex]