Secant Method

#include<stdio.h>
#include<conio.h>
#include<stdlib.h>
#include<math.h>

float function(float);
int main() {
    float a, A, b, B, c, C, tc, m;
    printf("Enter values of x1 and x2:\n");
    scanf("%f%f",&a,&b);
    A=function(a);
    B=function(b);
    if(A==B){
        printf("Error, Enter valid values.");
        exit(1);
    }
    tc=b;
    do {
        A=function(a);
        B=function(b);
        c=(((a*B)-(b*A))/(B-A));
        a=b;
        b=c;
        m=tc-c;
        tc=b;
    }while(fabs(m)>0.0009);
    printf("\n\nThe root is: %.4f",c);
    getch();
}

float function (float x) {
    return ((x*x)-(8*x)-14);
}