# Math

posted by
**Nicole**
.

Can someone walk me through these becuase I'm just not getting it....

Let f(x)= 3 x 4^x.

A.) 16f(x)= f(x+2)

B.) f(x)= f(x-1)

The quickest way to answer this question is to try different test values for x.

My favorite was the number 13.

Set x to 13, and see if A and/or B hold true.

You should also test with x as some other arbitrary values, such as pi or -1.

I don't think I'm really getting what you are saying. I thought that we were supposed to plug in 3 x 4^x in for f(x) in the equation, but after that point I get really confused....

For A.) with what we're given for f(x), we have 16*(3*4^x)=3*4^(x+2) or

48*4^x=3*4^x *4^2=48*4^x This appears to be true for all x therefore A) is an identity.

For B.) we have 3*4^x=3*4^(x-1) or

4^x=4^(x-1), or 4^x=4^x *(1/4) Can any x satisfy this equation?

You should observe that we look at what's in the placeholder for the argument x and substitute that into the expression; (x+2) in part A and (x-1) in part B.

Thanks,this really helped me

what word do you call the numbers that can`t be arranged into 2-row arrays

I thought someone answered this below -and correctly too I might add.

It would be a two row matrix, but you would still need to specify the number of columns as well.

The term array is more commonly used in computer science, while matrix is more common to math, specifically linear algebra. I'm not aware of any significant difference between the two terms either.

what is an array

arrays are arranged dots that are like 2*8

array would have 16 dots.

it's hard to explain!

sorry