SOLUTION: How do you write an equation for this table? X=1, 2, 3, 4, 5, 6, 7 Y=1, 3, 7, 15, 31, 63, 127

Algebra ->  Expressions-with-variables -> SOLUTION: How do you write an equation for this table? X=1, 2, 3, 4, 5, 6, 7 Y=1, 3, 7, 15, 31, 63, 127      Log On


   

Question 565392: How do you write an equation for this table?
X=1, 2, 3, 4, 5, 6, 7
Y=1, 3, 7, 15, 31, 63, 127
Answer by Edwin McCravy(20064) About Me  (Show Source):
You can put this solution on YOUR website!
X=1, 2, 3, 4, 5, 6, 7
Y=1, 3, 7, 15, 31, 63, 127
If you look at the Y-values, you will discover that
each one is one less than the corresponding term 
of this sequence:

2, 4, 8, 16, 32, 64, 128

which are the 1st, 2nd, 3rd, 4th, etc. powers of 2.

So the X-th term of the given sequence is 1 less than
2X.  So the equation you're looking for is:

Y = 2X - 1

You just have to be observant and familiar with the
various powers of small numbers to do problems like these.

Edwin