Hi Margaret;
For the first equation, the denominator, also known as the divisor, is g. No denominator can be zero. Henceforth, this is the only limitation on the domain...
(infinity,0)(0,+infinity)
Please note that the parentheses, as opposed to brackets, indicate that the zero is NOT included.
For the second equation, let's look at the denominator/divisor...
k^{2} + k  42
Let's factor.
For the FOIL...
FIRST must be...(k)(k)=k^{2}
OUTER and INNER must addup to 1k or k.
LAST...(6)(7).
(k+6)(k7)
Let's FOIL...
FIRST...(k)(k)=k^{2}
OUTER...(k)(7)=7k
INNER...(6)(k)=6k
LAST...(6)(7)=42
k^{2}7k+6k42
k^{2}7k42
(k+6)(k7)
Neither parenthetical equation can result in zero...
k+6=0
k=6
and
k7=0
k=7
Domain is...
(infinity,6)(6,7)(7,+infinity)
Parentheses indicate that neither 6 nor 7 are included.
AS PER STEVE'S COMMENT, I MADE THE CORRECTION HEREIN.
12/15/2013

Vivian L.
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