COding help, output is wrong

[mattkeem]

double getPaymentAmount(double interest, int numberOfMonths, double principal)
{
	double getPaymentAmount;
		getPaymentAmount = (powf((1+interest),numberOfMonths)/
							(powf((1+interest),numberOfMonths)-1)
							*principal*interest);
							
	return getPaymentAmount;
}
//----------------------------------------------------------------------------
//
//----------------------------------------------------------------------------
double getLoanAmount(double interest, int numberOfMonths, double payment)
{
	double getLoanAmount;
		getLoanAmount = (powf((1+interest),numberOfMonths) - 1*payment)/
						(interest*powf((1+interest),numberOfMonths));

	return getLoanAmount;

}
//----------------------------------------------------------------------------
//
//----------------------------------------------------------------------------
int getNumberOfMonths(double interest, double payment, double principal)
{
	int getNumberOfMonths;
		getNumberOfMonths = (log(payment)-log(payment-(principal*interest))) /
							(log(1+interest));

	return getNumberOfMonths;

payment = (1 + i)^ months * principal * i

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(1 + i) months - 1


principal = (1 + i )^ months - 1 * payment

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i * (1 + i ) months


months = log( payment ) - log( payment - (principal * i ))

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log( 1 + i )

this is the regular formula. can someone tell me what im doing wrong here?