Question

A= (4,5) B= (7,-9) what is AB ?

Answer 1

If you are needing to find the distance between the two points, you must use a simple formula, cleverly named, the distance formula. Since I can't input special characters into the answer box, I'll explain it the best I can.

( The square root of (  (x - x)^2 + (y - y)^2 )  )

First, we need to find the first x subtracted from the second x, as so:
(4,5) and (7,-9)

4 - 7 = -3

Now, we square the -3.

-3^2 = 
-3 * -3 = 9

Next, we have to find the first y subtracted from the second y.
(4,5) and (7,-9)

5 - (-9) = 14

Now, we square the 14.

14^2 =
14 * 14 = 196

Let's see how the numbers fit in the formula:

sqrt((x - x)^2 + (y - y)^2)

sqrt((4 - 7)^2 + (7 - (-9))^2)

sqrt((-3)^2 + (14)^2)

sqrt( 9 + 196 )

This is where we currently are in the formula, all we have to do now is square root the total of 9 + 196.

sqrt( 9 + 196 )
sqrt( 205 )

The square root of 205 = 14.31782106...

There are a few answers you can consider:

1) sqrt(205)
2) 14.32 units
or
3) 14.31782106

Depending on the answer you desire, use the one that sounds the most correct to you. Although all three are correct, it may not be the answer you require. 

Hope I could help! If my math is incorrect, or I provided answers you were not looking for, please let know! However, if my answer is correct and well explained, please consider marking my answer as Brainliest! :)

Have a good one.
God bless!