Annalise makes rectangular patchwork quilts out of leftover fabric scraps. The first scrap she is using to make a quilt has a width of 2x feet and a length of 5x feet. When finished, the entire quilt will be 5 feet wider and 3 feet longer than the first fabric scrap used. Which of the following functions will give the area, f(x), of the quilt in square feet?

A.
f(x) = 10x2 + 25x + 15
B.
f(x) = 10x2 + 15
C.
f(x) = 10x2 + 31x + 15
D.
f(x) = 10x2 + 16x + 15

1 answer

To find the function that represents the area \( f(x) \) of the quilt, we first need to determine the dimensions of the quilt based on the information provided.

  1. The dimensions of the first scrap:

    • Width = \( 2x \) feet
    • Length = \( 5x \) feet
  2. The area of the first fabric scrap: \[ \text{Area of the first scrap} = \text{Width} \times \text{Length} = 2x \times 5x = 10x^2 \text{ square feet} \]

  3. The quilt will be 5 feet wider and 3 feet longer than the first scrap:

    • Width of the quilt = Width of the scrap + 5 = \( 2x + 5 \) feet
    • Length of the quilt = Length of the scrap + 3 = \( 5x + 3 \) feet
  4. Now, we calculate the area of the quilt: \[ \text{Area of the quilt} = \text{Width of the quilt} \times \text{Length of the quilt} \] \[ \text{Area of the quilt} = (2x + 5)(5x + 3) \]

  5. We now expand this product: \[ (2x + 5)(5x + 3) = 2x(5x) + 2x(3) + 5(5x) + 5(3) \] \[ = 10x^2 + 6x + 25x + 15 \] \[ = 10x^2 + 31x + 15 \]

Therefore, the function that gives the area of the quilt in square feet is: \[ f(x) = 10x^2 + 31x + 15 \]

The correct answer is C.