DaniWeb IT Discussion Community - Applet - Graphing Quadratic Function Help

Hi!
Im making an applet to graph a quadratic function...now im not going to be rude and say "tell me how to do it!" but i was just wondering if i could get some assistance on making it...
Now of course, i've had a go at it, and i've made an applet to display the z intercepts, y intercept, and vertex (turning point). This is determined by the user inputs of the three coefficients a, b, and c.
First question, is this all the information i will need?
Secondly, i am struggling to figure out how to put this information into a graph and make it a parabola...
Thank you very much for your help!
Ps. my applet is below if you wish to have a look, i've made a crude graph if that helps as well...

import java.applet.*;

import java.awt.*;

import java.awt.event.*;

public class Graph2 extends Applet implements ActionListener {

    TextField aInput, bInput, cInput;

    double a, b, c;

    boolean notFirst;

    Button calcButton;

    int size = 400;

    public void init() {

        setLayout(null);

        resize(600, 500);

        Label labelA = new Label("Value a:");

        labelA.setBounds(412, 40, 50, 20);

        Label labelB = new Label("Value b:");

        labelB.setBounds(412, 70, 50, 20);

        Label labelC = new Label("Value c:");

        labelC.setBounds(412, 100, 50, 20);

        aInput = new TextField("2", 5);

        aInput.setBounds(470, 40, 80, 20);

        bInput = new TextField("5", 5);

        bInput.setBounds(470, 70, 80, 20);

        cInput = new TextField("-12", 5);

        cInput.setBounds(470, 100, 80, 20);

        calcButton = new Button("Solve");

        calcButton.setBounds(460, 130, 45, 20);

        add(labelA);

        add(aInput);

        add(labelB);

        add(bInput);

        add(labelC);

        add(cInput);

        add(calcButton);

        aInput.addActionListener(this);

        bInput.addActionListener(this);

        cInput.addActionListener(this);

        calcButton.addActionListener(this);

        notFirst = false;

    }

    public void makeGraph(Graphics g) {

        g.setColor(Color.lightGray);

        // Draw grid

        for (int y = 0; y <= size; y = y + 10) {

            g.drawLine(1, y, size, y);

        }

        for (int x = 0; x <= size; x = x + 10) {

            g.drawLine(x, 1, x, size);

        }

        g.setColor(Color.red);

        // Draw y axis

        g.drawLine(size / 2, 0, size / 2, size);

        for (int i = 0; i <= size; i = i + 20) {

            g.drawLine(size / 2 - 5, i, size / 2 + 5, i);

        }

        g.setColor(Color.blue);

        // Draw x axis

        g.drawLine(0, size / 2, size, size / 2);

        for (int j = 0; j <= size; j = j + 20) {

            g.drawLine(j, size / 2 - 5, j, size / 2 + 5);

        }

        g.setColor(Color.black);

        // Draw positive x axis numbers

        for (int n = 0; n <= 5; n++) {

            g.drawString("" + n * 2, (size / 2 - 4) + n * 40, size / 2 + 17);

        }

        // Draw negative x axis numbers

        for (int n = 1; n <= 5; n++) {

            g.drawString("-" + n * 2, (size / 2 - 6) - n * 40, size / 2 + 17);

        }

        // Draw positive y axis numbers

        for (int n = 1; n <= 5; n++) {

            g.drawString("" + n * 2, size / 2 - 21, (size / 2 + 5) - n * 40);

        }

        // Draw negative y axis numbers

        for (int n = 1; n <= 5; n++) {

            g.drawString("-" + n * 2, size / 2 - 23, (size / 2 + 6) + n * 40);

        }

    }

    public void paint(Graphics g) {

        int yValue = 180;

        makeGraph(g);

        g.drawString("y = ax\u00B2 + bx + c", 420, 20);

        if (notFirst) {

            double zero = ((( -b) + (Math.sqrt((b * b) - (4 * (a * c))))) / (2 * a));

            double zero2 = ((( -b) - (Math.sqrt((b * b) - (4 * (a * c))))) / (2 * a));

            g.drawString("a = " + a, 420, yValue);

            g.drawString("b = " + b, 420, yValue + 20);

            g.drawString("c = " + c, 420, yValue + 40);

            if (a == 0) {

                g.drawString("a Cannot Be 0", 420, yValue + 80);

            } else {

                if (((b * b) - (4 * a * c)) < 0) {

                    g.drawString("No Real Solution", 420, yValue + 80);

                } else {

                    g.drawString("Zero = (" + zero + ", 0)", 420, yValue + 80);

                    g.drawString("Zero = (" + zero2 + ", 0)", 420, yValue + 100);

                    g.drawString("Y Intercept = (0, " + c + ")", 420, yValue + 120);

                    double turnX = -b / (2 * a);

                    double turnY = c - (Math.pow(b, 2)) / (4 * a);

                    g.drawString("Vertex = (" + turnX + ", " + turnY + ")", 420, yValue + 140);

                    double d = (Math.pow(b, 2)) - 4 * a * c;

                    g.drawString("Discriminant = " + d, 420, yValue + 160);

                    if (a < 0) {

                        g.drawString("Parabola = Down", 420, yValue + 180);

                    } else {

                        g.drawString("Parabola Direction = Up", 420, yValue + 180);

                    }

                }

            }

        }

    }

    public void actionPerformed(ActionEvent e) {

        notFirst = true;

        if (e.getSource() == calcButton) {

            a = Double.parseDouble(aInput.getText());

            b = Double.parseDouble(bInput.getText());

            c = Double.parseDouble(cInput.getText());

            if (aInput.getText().equals("")) {

                a = 0;

            }

            repaint();

        }

    }

}

-Crawf