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Problem Flipping/Inverting Mortgage Formula


New member
Jul 18, 2014
Hi Forum,

I would really appreciate your help. I have a formula here that calculates the monthly payment amount for a loan:

P = ( r * A ) / ( 1 - (1+r)[SUP]-N[/SUP])

With: P=Payment Amount, r=Rate of Interest, A=Loan Amount, N=Number of Payments <not that this information is necessary to do the maths

However I need to find the value of N and I am really struggling in how to flip the formula to get that. I could do it if it was just multiply and divide but the negative power to is really driving me crazy. If you could show me how you did it that would be really helpful also. Thanks in advance! :)