Good question , don’t really know but use photo math or there’s an link for you
In this case we have an ARM fixed for 6 years and adjust after the initial first 6 years every 2 years after. The basic idea behind a ARM is that the interest changes periodically, but since our ARM is fixed for 6 years, our going to calculate the monthly payment during the initial period using the formula:

where

is the monthly payment

is the amount

is the interest rate in decimal form

is the number years
First we need to convert our interest rate of 4% to decimal form by dividing it by 100%:

We also know from our question that

and

, so lets replace those values into our formula to find the monthly payment:


We can conclude that the monthly payment during the initial period is $1071.58<span />
He increased 30% so that means he can bench press 180lbs
The pattern is:
( a - b )² = a² - 2 a b + b² ( square of last term of binomial - the missing term)
x² - 2 · 8 · x + 8² = x² - 16 x + 64 = ( x - 8 )²
The missing term is: 64