Answer:
y = -4x + 50
Explanation:
To write the function we'll use y = mx + b, where y is the distance the boat is away from shore, m is how many km/minute the boat moves at, x is how many minutes it's been, and b is how many km away from shore the boat was at the start. We already know the value of b is 50, so we can put that into the equation:
y = mx + 50
To find how many km the boat moves per minute, let's use the given amount of minutes and km (9, 14) and put them into the equation:
14 = m(9) + 50
Now let's solve for m:
14 = 9m + 50
Subtract 50 from both sides to isolate the 9m:
14 - 50 = 9m + 50 - 50
- 36 = 9m
divide both sides by 9 to isolate the m:
-36/9 = 9m/9
-4 = m
The boat moves at -4 km/minute, which is the same thing as saying that after 1 minute passes, the boat gets 4km closer to the shore. Now we can input this value into the equation and we have our answer:
y = -4x + 50