? 
Please help me with this problem..........
You will implement a java class
QuadFunc for representing and manipulating quadratic functions.You will do this by completing a template of the class that I have created and which
specifies the API of the class. You may
not alter the method prototypes specified in the template.You may however add private methods as needed to the class. Note also that you will have to
determine the data members of the class and add them.
/**
* Class for representing quadratic functions (degree 2 polynomials).
* Allows numerous natural operations on such functions including
* differentiation, evaluation, approximate integrals, addition of
* two quadratic functions, etc
public class QuadFunc
{
// Your instance variables declared here
/**
* Default Constructor for objects of class QuadFunc.
* Creates a quadratic function y = x^2
*/
public QuadFunc(){
// YOUR CODE HERE
}
/**
* Constructor for objects of class QuadFunc.
* Creates a quadratic function y = ax^2 + bx + c
*/
public QuadFunc(double a, double b, double c){
// YOUR CODE HERE
}
/**
* Evaluates a quadratic function for given x-value
*
* @param x x-value at which to evaluate the function
* @return the value of the function evaluated at x.
*/
public double eval(double x){
// put your code here
return 0; // remove this; it is here just to make sure it compiles
}
/**
Function is multiplied by coeff (this is a mutator function).
E.g., if f(x) = 2x^2 - 3x + 7 and coeff == -1, f(x) becomes
-x^2 + 3x - 7.
*/
public void multByScalar(double coeff) {