Help me please! i keep on seeing this error!

cannot convert `double' to `double*' for argument `1' to `double get_fx(double*, int, double, double, double)'

here is my code.
please help me fix it

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

using namespace std;

int input_pol(double coef[],int& Pow);
double get_fx(double coef[],int Pow,double l,double x,double fx);

double falsi(double*, double);

const int MAX = 1000;


int main()
{

double coef[1000];
double xnew[MAX], xplus[MAX], xminus[MAX];
int imax, Pow;

input_pol(coef,Pow);




cout << endl;
cout << "Enter first guess: ";
cin >> xplus[0];
cout << endl;
cout << "Enter Second guess: ";
cin >> xminus[0];
cout << endl;
cout << "Set maximum iteration: ";
cin >> imax;

for(int i = 0; i < imax; i++)
{
xnew[i] = falsi(xplus[i], xminus[i]);

if(get_fx(xnew[i])> 0)
{
xplus[i+1] = xnew[i];
xminus[i+1]=xminus[i];
}
else
{
xminus[i+1] = xnew[i];
xplus[i+1]=xplus[i];
}
}
cout << endl << endl;
for(int i = 0; i < imax; i++)
{
cout.setf(ios::fixed);
cout.setf(ios::showpoint);
cout.precision(20);
cout << xnew[i] << endl;
}

cout << endl << endl << endl;
cout << "The Approximate root is: ";

cout.setf(ios::fixed);
cout.setf(ios::showpoint);
cout.precision(20);
cout << endl << endl << xnew[imax - 1];

cin.get();
cin.get();

return 0;
}
int input_pol(double coef[],int& Pow)
{
cout<<"Enter the highest degree in the polynomial: ";
cin>>Pow;
cout<<endl;
for(int i=Pow;i>=0;i--)
{
cout<<"Enter the coefficient of each term with thier corresponding sign."<<endl;
cout<<i+1<<" term: ";
cin>>coef[i];
cout<<coef[i]<<"x^"<<i<<endl;
}
}
double get_fx(double coef[],int Pow,double l,double x,double fx)
{

for(int i=Pow;i>=0;i--)
{
l+=(coef[i]*pow(x,i));
fx=l;
}
return fx;
}

double falsi(double* xp, double xm)
{
return xp - get_fx(xp) *(xp - xm)/(get_fx(xp) -get_fx(xm));
}