The chart is not drawn using QPainter::drawPoint(), what should I do?

Question

Qt

I draw a graph by points, "x" varies from -2 to 3, "y" is equal to the formula that is given by the task, but the whole point is that when I try to draw this point, I simply have nothing, nothing is drawn.

for(float i = -2; i <= 3; i+=0.01){
        y = ((qExp(2*i)/4) + (C/qExp(2*i)) - 2000);
        painter.drawPoint(QPoint(width()/2, height()/2)+QPoint(i, y));
    }