Given that 2x-5=3(2x-2)-15, WHAT IS THE EVALUATION OF 2X+1?

Question

what is the evaluation?

Answer 1

Let u = 2x+1. Then 2x-5 = 2x+1-6 = u-6, and 2x-2 = 2x+1-3 = u-3.

So,

 2x-5=3(2x-2)-15 becomes,

u-6 = 3(u-3)-15=> u-6 = 3u-24

=> 18 = 2u

=> u = 9

Answer: 2x+1 = 9

Answer 2

2x-5=3(2x-2)-15

2x-5=6x-6-15

2x-5=6x-21

21-5=6x-2x

16=4x

x=4

2x+1=2(4)+1=8+1=9

Answer 3

One thing which might be confusing in this problem is the wording. "What is the evaluation of 2x+1" is just funky math-speak for "what number is 2x+1 once you plug in x." To do this, we can solve the equation they give us, and then we'll plug in x.

 

 

Let me show you a similar example: Given that  3x - 2 = 4(2x - 2) - 14, what is the evaluation of 3x + 2?

 

We'll start by solving for x:

3x - 2  =  4(2x - 2) - 14

3x - 2  =   8x - 8    - 14

3x - 2  =  8x - 22

      +22        +22

 

3x + 20  =  8x

-3x             -3x

 

20  =  5x

/5       /5

 

4    =  x

 

Now we know that x is 4. Therefore, 3x+2 evaluates to  3(4) + 2,  which is better known to its friends as 14.

 

 

Take home message: The phrase "evaluation" means "what number do you get when you plug in for all of the variables." Hopefully this is enough to help you make some progress. :-)