283,079 views
29 votes
29 votes
What is f^-1(-7) plus f(-7)? I need help answering this question

What is f^-1(-7) plus f(-7)? I need help answering this question-example-1
What is f^-1(-7) plus f(-7)? I need help answering this question-example-1
What is f^-1(-7) plus f(-7)? I need help answering this question-example-2
User ZeroKelvin
by
2.4k points

1 Answer

20 votes
20 votes

Answer:

13

Explanation:

You want the sum of f^-1(-7) and f(-7) given the function definition in the table.

Inverse function

The inverse function f^-1(x) consists of ordered pairs that are the reverse of the ordered pairs (x, f(x)). That is ...

(x, f^-1(x)) ≡ (f(x), x)

Another way to describe f^-1(x) is "the value of z that gives f(z) = x". This means f^-1(-7) is the value of x that gives f(x) = -7. That x-value is 6:

f^-1(-7) = 6 . . . . . from the 4th column of the table

Function value

We can read the function value directly from the table:

f(-7) = 7 . . . . . . the first column of the table

Sum

Then the sum of interest is ...

f^(-1)(-7) +f(-7) = (6) +(7)

f^(-1)(-7) +f(-7) = 13

__

Additional comment

The inverse function ordered pairs are ...

(x, f^-1(x)) = {(7, -7), (12, 11), (8, -13), (-7, 6), (13, 5)}