write a rule

Question

how do I write a rule for:

 

    x   -1, 0, 1, 2

    y    1, 3, 9, 27

 

 

I think it is x add 1, and y multiply by 3

 

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  x   -1, 0, 1, 2

  y    3, 1, 1/3, 1/9

 

How do I write a rule for this function?

Answer 1

I think you mean equation, expressing y in terms of x. But that's just terminology. Anyway, you're pretty close, because you figured out they multiply by 3. That means that y is some power of three.

 

In this case, when x=0, y=3. So 3=3^(0+1). let's check out work.

(-1,1) : 1=3^(-1+1). Check.

(1,9) :  9 = 3^(1+1). Yes.

(2,27) : 27=3^(2+1). Yes!

 

So: y=3^(x+1). Be sure to check all the numbers to be sure!