Rectangle Perimeter Problem: Solving with Dimensions (X+5) and (X-1)

Question

Look at the following rectangle:

AAABBBCCCDDDX+5X-17

The area of the rectangle is 7.

What is the perimeter of the rectangle?

Video Solution

Solution Steps

00:00 Calculate the perimeter of the rectangle
00:03 Use the formula for calculating the area of a rectangle (side multiplied by side)
00:14 Substitute appropriate values according to the given data and solve for X
00:30 Open parentheses properly, multiply each factor by each factor
00:50 Arrange the equation so that one side equals 0
00:58 Collect like terms
01:07 Use trinomial method and pay attention to coefficients
01:11 We want to find 2 numbers whose sum equals 4(B)
01:21 And their product equals (-12)(C)
01:24 These are the appropriate numbers, let's put them in parentheses
01:33 Find the solutions that make each factor equal to zero
01:40 X must be positive since it's a value of a side
01:44 Therefore this solution is the solution for X
01:54 This is the value of X, let's substitute to find the side length
02:06 Opposite sides are equal in a rectangle
02:26 The perimeter of the rectangle equals the sum of its sides
02:36 Insert the appropriate values into the formula and solve for the perimeter
02:47 This is the solution

Step-by-Step Solution

To solve this problem, we'll need to find the value of X X and then use this value to find the perimeter of the rectangle. Follow these detailed steps:

  • Step 1: Set up the equation for the area.
    Given the area of the rectangle is 7, and the sides are (X+5) (X + 5) and (X1) (X - 1) , the equation becomes:

(X+5)(X1)=7(X + 5)(X - 1) = 7
Expanding the left side, we have: X2+5XX5=7 X^2 + 5X - X - 5 = 7 X2+4X5=7 X^2 + 4X - 5 = 7

  • Step 2: Simplify and solve the quadratic equation.
    By moving all terms to one side, we have:

X2+4X57=0 X^2 + 4X - 5 - 7 = 0 X2+4X12=0 X^2 + 4X - 12 = 0

  • Step 3: Factor the quadratic equation.
    We factor the equation as:

(X+6)(X2)=0 (X + 6)(X - 2) = 0

  • Step 4: Solve for X X using the zero-product property.
    The solutions for X X are:

X+6=0X=6 X + 6 = 0 \Rightarrow X = -6 X2=0X=2 X - 2 = 0 \Rightarrow X = 2

  • Step 5: Use the positive X X value to find the perimeter.
    Since dimensions cannot be negative, X=2 X = 2 . Thus, the rectangle’s dimensions become:

Length=X+5=2+5=7 \text{Length} = X + 5 = 2 + 5 = 7
Width=X1=21=1 \text{Width} = X - 1 = 2 - 1 = 1

  • Step 6: Calculate the perimeter using the dimensions.

P=2×(Length+Width)=2×(7+1)=2×8=16 P = 2 \times (\text{Length} + \text{Width}) = 2 \times (7 + 1) = 2 \times 8 = 16

Therefore, the perimeter of the rectangle is 16.

Answer

16