Question

ANSWERS GET MEDALS!!
Find the Domain
1. f(z)=√((1-z)/(z+2))
2. √-x^2-15x-54
3. y=√-x^2+12x-27

Answer 1

1) First: you can't divide by 0, so
z+2 can not be 0,
then z not equal to (-2)
second condition - expression under sq. rt >=0

Answer 2

for that - put 2 systems together:
a) 1-z>=0 and z+2>=0
b) 1-z<=0 and z+2<=0
solve it

Answer 3

should get:
z : (-2,1]

Answer 4

ok thank you thats what i got for that one as well what about the other two?

Answer 5

2) \[=\sqrt{-(x+9)(x+6)}\]
now you have to solve it that the expression under (all!) will be >=0
which means that one of the multiples needs to be negative

Answer 6

or:
a) x+9<=0 and x+6 >=0
b) x+9 >=0 and x+6<=0

get your answer & let's compare

Answer 7

what did you get?

Answer 8

9,6

Answer 9

i got:
x: [-9,-6] and another set is empty

check signs in your solution :)

Answer 10

3)\[\sqrt{-(x-9)(x-3)}\]
need to do the same as in 2)
do you want to try & will compare notes?

Answer 11

[3,9]..?

Answer 12

should have:
a) x-9>=0 and x-3<=0
b) x-9 <=0 and x-3 <=0

You are right!!

Answer 13

sweet!! thanks man!!

Answer 14

:))