Final answer:
The correct equation to find the dimensions of the horse paddock with an area of 1,800 square feet, using the side of the barn as one side and letting x represent the width, is -2x² + 120x = 1800, which is option (a).
Step-by-step explanation:
To determine which equation can be used to find the dimensions of the horse paddock with an area of 1,800 square feet, where Jill is using the side of the barn as one side of her paddock, we need to set up an equation that accounts for the perimeter and area of the paddock. Since the fencing will only be covering three sides (2 widths and 1 length), if we let x represent the width, then the remaining length would be 120 - 2x feet because Jill has 120 feet of fencing in total.
The area of the paddock can be found by multiplying the width by the length. Therefore, the area A can be expressed as:
A = x * (120 - 2x)
This simplifies to:
A = 120x - 2x²
Since we know the area is supposed to be 1,800 square feet:
1800 = 120x - 2x²
And if we rearrange the terms to match the given equations, we get:
-2x² + 120x = 1800
Therefore, the correct equation to find the dimensions of the horse paddock when the area is 1,800 square feet, letting x represent the width, is:
-2x² + 120x = 1800
Which corresponds to option (a).