Question

I'm using DEV C++ to write my programs for my homework in my very first programming class. My professor is rather difficult to understand. I need help!

Answer 1

#include <iostream>
#include <math.h>

using namespace std;

int main()

{
char ch;
double a, x, b, c;

x = (-b + sqrt(b^2 - 4*a*c))/(2*a)


cout<<" **** Homework 4 - EGR 126-11 ****"<<endl<<endl<<endl;
cout<<"solves for x in the equation: a*x^2 + b*x + c = 0."<<endl;
cout<<"The user should enter values for a, b, and c (use double data types). " <<endl<<endl;

cout<<"Enter a number for 'a'... "<<endl;
cin>> a;
cout<<"Enter a number for 'b'... "<<endl;
cin>> b;
cout<<"Enter a number for 'c'... "<<endl;
cin>> c;

if (a == 0) && (b == 0) cout<<"This condition is 'true'... "<<endl;
else cout<<"This condition (a == 0) && (b == 0) is 'false... " <<endl;


switch (ch)
{
case 0:
cout<<" a = 0 & b =0, there is no solution for 'x'... "<<endl;
break;
default:
cout<<" 'a' and 'b' should be greater or less than 0... "<<endl;
}


cout<<" Press 'e' to exit... "<<endl;
cin.get(ch);

return (0)

}

*** this is what I currently have and I wanted to see if i can compile and run it but I'm getting so many errors. The main objective here is that I have to solve for x from the quadratic equation a*x^2 + b*x + c = 0. My program must allow users to enter numbers for a, b, and c to solve for 'x'.
There are five possible outcomes for x:
1. if a = 0 and b = 0, no solution can be found for x
2. if a = 0 and b != 0, x = -c/b
3. if a != 0 and (b^2 - 4*a*c) = 0, x1 = x2 = -b/(2*a)
4. if a != 0 and (b^2 - 4*a*c) > 0, x1 = (-b + sqrt(b^2 - 4*a*c))/(2*a)
x2 = (-b - sqrt(b^2 - 4*a*c))/(2*a)
5. if a != 0 and (b^2 - 4*a*c) < 0, x1 = (-b/(2*a) + (sqrt(4*a*c - b^2)/(2*a)) "i"
x2 = (-b/(2*a) - (sqrt(4*a*c - b^2)/(2*a)) "i"
where "i" = sqrt(-1); "i" and "+" in text
only; real and imaginary parts must
be calculated separately.

I have to use the if-else code but I don't know where to start and I don't know how to tie things in together.

Answer 2

My errors that i don't know how to fix:

x = (-b + sqrt(b^2 - 4*a*c))/(2*a)
invalid operands of types `double' and `double' to binary `operator^'

if (a == 0) && (b == 0) cout<<"This condition is 'true'... "<<endl;
expected identifier before '(' token.

Answer 3

^ in c++ is a bitwise operator
http://www.cplusplus.com/doc/tutorial/operators/#bitwise

If you are trying to square the number, try and use the pow method
http://www.cplusplus.com/reference/cmath/pow/

Also, it might be important to have ((a == 0) && (b == 0)) inside of the same parenthesis. I'm guessing that the parser saw the parenthesis end ')' then came across the unexpected token '&&'.

My answers are more or less hunches, since I don't know c++.

Answer 4

@woodrow73 Thank you, putting a and b in the same parentheses actually allowed me to compile and run the program. I've been working on the homework for a while and i'm starting to patch things together i suppose. I hope i get this all figured out. I'm quite confused still but thanks for the help. I'll be checking the links.

Answer 5

Especially when you're confused, break the problem and what you're doing to solve it into smaller pieces. The smaller the easier.

BTW, in your code, I didn't see where x or ch were being assigned any value.