Question

whats the domain of square root of (x^2-81)

Answer 1

It's a polynomial. What do you think?

Answer 2

is it (-infinity, -9) and (9, infinity)

Answer 3

the expretion under square root can't be negative, do x^2-81>=0, or x^2>=81
can you finish this?

Answer 4

\[f(x)= \sqrt{x^2-81}\]

Answer 5

answer would be 9?

Answer 6

no

Answer 7

Anytime you take the squareroot of a number it equals positive and negative of that integer

Answer 8

(-infinity, -9] and [9, infinity)

Answer 9

okay so includes the -9 and 9 thank you!!

Answer 10

yes

Answer 11

Oh, I didn't notice the "square root of."

Answer 12

but @ParthKohli is right, because in the set I, it would be ok all R as domain

Answer 13

thank you very much to help me understand! wasn't sure if my answer was right or wrong! thank you!

Answer 14

try this one to see if u understood the concept fully
\[f(x) = \sqrt{81-x^2}\]

Answer 15

that would be [-9,9]

Answer 16

Correct!

Answer 17

haha thanks!

Answer 18

well done!