Help please

19 points

Domain questions are basically validity checks. Since you cannot have a negative number in a square root without creating an imaginary number, that takes out the bottom two.

A quick tip: substitute the value for x. If the equation is valid (no imaginary numbers, not dividing by 0, etc, that function has the given domain.

ex:

Negative square roots lead to imaginary numbers so this is not the domain for this problem. The Domain for this one is since that is the lowest possible value of x you can have that is valid.

To answer your question, since I assume you are pressed for time,

so the first one is the function that has the given domain.

a 4/6 = 9/12   not proportional

step-by-step explanation:

to find which are not proportional, we can use cross products

if it is true, they are proportional.   if it is not true, they are not proportional.

a 4/6 = 9/12

4* 12 = 6*9

48 = 54

not this is not proportional  

b 2/3 = 12/18  

2* 18 = 3 * 12

36 = 36

this is proportional

c 5/4 = 10/8  

5*8 = 4*10

40 = 40

this is proportional

d 7/5 = 35/25

7*25 = 5 * 35

175 = 175

is proportional

inch

step-by-step explanation:

yard and mile are too big.