7.5
Using the Pythagorean theorem you can determine this answer! Let me know if I’m wrong!
Answer: <em>"7 is a solution to the original equation. The value –1 is an extraneous solution."</em>
Step-by-step explanation:
The equation
can be solved by squaring both sides:

We can see that -1 and 7 are solutions, but make sure they are not extraneous by substituting them in the original equation:

The square root of 49 equals 7, but the square root of -1 is an imaginary number.
The correct choice is <em>"7 is a solution to the original equation. The value –1 is an extraneous solution."</em>
The answer to 19b is 35
i’m sorry i don’t know part A
You can eliminate 81 because we know 
The dot is on approximately 9.32 (my estimate) so I would square that number:
(9.32)² = 86.8624 so if you round this you get 87
Here we get the statement:
"sec^-1(0.5) is undefined"
And we want to see if this is true or false, so let's use the properties that we know to find that this is false.
Remember that the sec function is defined as:

Then we will have:

Then is really trivial to see that:

Then we can conclude that the function is not undefined at 0.5, so the statement is false.
Below you can see the graph of the given function, and you will see that it is never undefined.
If you want to learn more, you can read:
brainly.com/question/16453813