Posted by Angela on Sunday, July 24, 2011 at 8:20pm.
find the domains of the following functions:
a) f(x)=x^20
b) g(x)=1/(x3)
c) h(x)=1/(4x^2=21x18)
d) k(x)=sqrt (4x^221x18)
e) p(x)=1/sqrt(4x^221x18)

Pre Cal  Reiny, Sunday, July 24, 2011 at 9:18pm
a)  anything goes
b)  anything except x=3
c) we need factors of
4x^2  21x  18
= (x  6)(4x + 3)
so x ≠6 or x ≠ 3/4
d) Now the number inside the √ cannot be negative.
so x ≤ 3/4 or x ≥ 6
e) not the number inside cannot be zero or negative.
you do that one, let me know what you got.

Pre Cal  Angela, Sunday, July 24, 2011 at 9:23pm
isn't it the same as d, because the domain is looked at in the demoninatior?

Pre Cal  Reiny, Sunday, July 24, 2011 at 9:30pm
no,
in d) the √ was a numerator while in e) it is now a denominator.
So now we also have to worry about division by zero.
btw, I just noticed a typo which probably caused confusion.
e) should have said:
" e) note that the number inside cannot be zero or negative. "
Of course the result is zero when x=6 or x=3/4, which we cannot have
so just make it : x < 3/4 OR x> 6

Pre Cal  Angela, Sunday, July 24, 2011 at 9:32pm
and x<3/4 or x>6 is the answer?

Pre Cal  Reiny, Sunday, July 24, 2011 at 9:42pm
If you understood what I worked for you, you should have realized that I missed the negative sign in x<3/4 as a typo.
so .......
x < 3/4 OR x > 6

Pre Cal  Angela, Sunday, July 24, 2011 at 9:44pm
Oops. sorry i was distracted while writing and forgot to put the negitive.

Pre Cal  Dalidah, Tuesday, August 16, 2011 at 4:54pm
this is wrong
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