The sum of angles of all triangles is 180
Answer:
C
Step-by-step explanation:
The Rnge of f(x)=1/7(9)^x is 0 to infinty
y|y>0
Answer: -2√7
Step-by-step explanation:
For this case, we have the following equation (according to the comments):

First, we factor the quadratic expression in the denominator:

Then, we multiply both sides of the equation by (a-2) (a + 2):

Later, canceling similar terms we have:

We do distributive property on the left side of the equation:

By grouping variables and constant terms we have:

Rewriting we have:

Finally, by clearing "a" we have:

Note: the value of a is a extraneous solution because it makes the denominator of the original equation equal to zero.
Answer:
the student correct, but the value of a= -2 is an extraneous solution