1. Solve for y in each equation, then inspect the slope of the two lines:

- If they are the same, then they are parallel

- If their product is -1, then they are perpendicular

- If they are not equal and their product is not -1, then they are neither parallel nor perpendicular.

2. Note that

Plug in in and , then find their products.

3.

The domain is the set of real numbers for which the composite function is defined. The function is defined for all x such that

4. It's a linear function, so it is injective. To check, graph the function and apply the horizontal line test (If the horizontal lines intersect the curve at most one point, then it is one-to-one. Otherwise, it's not injective.)