eff

#include < stdio.h > 
#include < math.h > 
#define FMT "%-10.5g"
float f(float x) {
    return x * x - x - 1.0;
}
float erfen(float a, float b, float eps) {
    float f1,
    t,
    x,
    h;
    x = (a + b) / 2.0;
    f1 = f(a);
    t = f(x);
    h = (b - a) / 2.0;
    while (h >= eps) {
        if (fabs(t) < 1e-6) return x;
        if (t * f1 < 0.0) b = x;
        else {
            a = x;
            f1 = t;
        }
        x = (a + b) / 2.0;
        t = f(x);
        h /= 2.0;
    }
    return x;
}
void main() {
    printf("\nZheng Gen:\n");
    printf(FMT, erfen(0.0, 2.0, 0.05));
}