Which relation is a function?
a. {(2, 3), (1, 5), (2, 7)}
b. {(-1,5), (-2, 6), (-3, 7)}
oc. {(11, 9), (11, 5), (9,3)}
d. {(3, 8), (0, 3), (3,-2)}

B is a function.

Step-by-step explanation:

A relation that is a set of points is a function if all the x's are different.  Each ordered pair in the set (excluding the duplicates if any) all have to have a distinct x.

For example if someone ask you if this is a function they are trying to trick you:

{(4,5),(1,3),(4,5)}.

They are trying to trick you because they listed the element (4,5) twice.

The set is really {(4,5),(1,3)}.

This would be a function because all the x's are distinct, ex 4 is different than 1.

Let's look at your choices:

A This is not a function because you have two pairs with the same x-coordinate.

B This is a function.  There are no repeats of any x,

C This is not a function because you have 11 as x twice.

D This is not a function because x=3 happens twice.

If the same x happens more than once than it isn't a function.  

step-by-step explanation:

the original amount doesn't ''re just looking for the time it takes for 1/2 of the substance to we have

(1/2) =)     take the ln   of both sides

ln (1/2)   = )   and we can write

ln(1/2) = ) lne     and lne   = 1     so we have

ln(1/2) = -.1092t     divide both sides by -.1092

t = ln(1/2)/-.1092 = about 6.347 days = about 6.3 days (rounded)