Question

() and () are inverses of one another and drawn on the same graph with the same scale on both the horizontal and vertical axis. Which of the following would be true?

A.
By reflecting the entire coordinate grid over the line =, () would land on ().

B.
() is the same as (), translated up 3 units.

C.
By rotating () 90° clockwise around the origin you would get ().

D.
By rotating () 180° clockwise around the origin you would get ().

Answer 1

Answer: Option A.

Step-by-step explanation:

We have the functions f(x) and g(x), that are inverses between them.

This means that if:

f(x) = y

then:

g(y) = x.

now, remember that:

When we have a point (x, y), and we reflect it over the line y = x, our new point will be (y, x).

So before we whe had:

f(x) = y.

and now in that same place, we have:

g(y) = x.

So the old graph of f(x) now coincides with the graph of g(x). (And the old graph of g(x) now coincides with the graph of f(x) )

So A is true.

B) This depends on the function:

if we have f(x) = x  + 1.5

then f(0) = 1.5

now we want that:

g(1.5) = 0, then we can write:

g(x) = x - 1.5

Now f(x) and g(x) are inverses, and we would have that:

f(x) = g(x) + 3.

So f(x) is g(x) translated up by 3 units, but this is a particular case, not a general one, so B is not always true.

C and D) When we do rotations of 90° or 180°, we are effectively changing the quadrant of our point. so rotations will cause not only changes as the reflection over the x = y line, those will also cause changes in the sign of our variables, so, while for some functions f(x) and g(x) we can have that the rotations will map one into the other, this is not the general case.