Final answer:
The constant of variation for the ordered pairs (10, -2) and (90, -18) is -0.2. The direct variation equation is y = -0.2x.
Step-by-step explanation:
To identify the constant of variation (k) for the direct variation equation, and then write the equation, follow these steps:
- Understand that a direct variation between two variables x and y can be represented by the equation y = kx, where k is the constant of variation.
- Use the given ordered pairs (10, -2) and (90, -18) to find the constant of variation by dividing the y-value of the pair by its corresponding x-value.
- For the first pair (10, -2), divide -2 by 10 to get k = -0.2.
- Confirm that k is consistent with the second pair by dividing -18 by 90, which also gives k = -0.2.
- Now that we've established the constant of variation is -0.2, we can write the direct variation equation as y = -0.2x.