By doing so, they provide the illusion that the payments are cheaper then 1000 dollars, because 50 looks very small, when in reality it's $100 more then what the mattress is actually worth.
I'm going to answer this as a process going down:
√x+1=6 The statement
x+1=6² Move the sqrt to the other side
x=6²-1 As well as the +1
x=36-1 Simplified the equation
x=35 Final answer
