0

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