# Thread: X and Y-axis in sketching

1. ## X and Y-axis in sketching

how do you know the x and y axis for the maximum point in sketching?

for example, y=-3x^2 + 5x -7

i completed the square and got -3(x-5/6)^2 + 109/12

so, i know the graph touches the y inetcept at -7, but is the x-axis of the turning point 5/6 or 3 x 5/6? and for the Y, how do you find it? i thought it was 109/12, but when i tried it online the graph looked different ( attached the online graph).

2. ## Re: X and Y-axis in sketching

I'm not quite sure what you are asking. This is a downward facing parabola as you know. Did you want the y value for the vertex? $y(5/6) = -3(5/6)^2 + 5(5/6) -7 = \frac{-59}{12}$. So that the maximum occurs at $(x,y)=(5/6, -59/12)$