You can put this solution on YOUR website! maximum/minimum will be turning point. Differentiate the function which is what I think you mean gives you a gradient of x-1, so will have a minimum (minimum as is positive so a bowl shape with a minimum and no maximum) at x=1, at which point y = -4.5.
zeros;
x=0, y=-4 clearly
y=0, - I multiplied by 2 to make easier
0=(x-4)(x+2), x= 4 or -2
Line of symmetry I am fairly sure it doesn't have as it is a function of x which is an odd function, and x^2 which is even.7
Drawing the graph should be fine now you know where it crosses the axes.