Math Problem Statement

The area of a rectangle is 28y^2, and the length of the rectangle is 1 more than twice the width. Find the dimensions of the rectangle.

Solution

To solve this problem, we will define the width and length of the rectangle in terms of a variable and then use the information provided to set up and solve an equation.

Step-by-Step Solution:

  1. Define the variables:

    • Let ww be the width of the rectangle.
    • According to the problem, the length ll is "1 more than twice the width". So, we can write this as: l=2w+1l = 2w + 1
  2. Set up the equation for the area:

    • The area AA of a rectangle is given by the product of its length and width: A=l×wA = l \times w
    • We know the area is 28y228y^2. Substitute the expressions for ll and AA into the equation: 28y2=(2w+1)×w28y^2 = (2w + 1) \times w
  3. Expand and simplify the equation:

    • Expand the equation: 28y2=2w2+w28y^2 = 2w^2 + w
    • Rearrange the equation to set it equal to 0: 2w2+w28y2=02w^2 + w - 28y^2 = 0
  4. Solve the quadratic equation for ww:

    • To solve for ww, use the quadratic formula w=b±b24ac2aw = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}, where a=2a = 2, b=1b = 1, and c=28y2c = -28y^2.
    • Plugging in the values: w=1±124×2×(28y2)2×2w = \frac{-1 \pm \sqrt{1^2 - 4 \times 2 \times (-28y^2)}}{2 \times 2}
    • Simplify under the square root: w=1±1+224y24w = \frac{-1 \pm \sqrt{1 + 224y^2}}{4}
  5. Determine the width ww:

    • Since the width must be a positive number, we take the positive root: w=1+1+224y24w = \frac{-1 + \sqrt{1 + 224y^2}}{4}
  6. Calculate the length ll:

    • Now, substitute ww back into the expression for ll: l=2w+1=2(1+1+224y24)+1l = 2w + 1 = 2 \left( \frac{-1 + \sqrt{1 + 224y^2}}{4} \right) + 1
    • Simplify this expression: l=2+21+224y24+1=2+21+224y2+44l = \frac{-2 + 2\sqrt{1 + 224y^2}}{4} + 1 = \frac{-2 + 2\sqrt{1 + 224y^2} + 4}{4} l=2+21+224y24=1+1+224y22l = \frac{2 + 2\sqrt{1 + 224y^2}}{4} = \frac{1 + \sqrt{1 + 224y^2}}{2}

Final Dimensions:

  • The width of the rectangle is: w=1+1+224y24w = \frac{-1 + \sqrt{1 + 224y^2}}{4}

  • The length of the rectangle is: l=1+1+224y22l = \frac{1 + \sqrt{1 + 224y^2}}{2}

Would you like more details or have any questions about this solution?

Related Questions:

  1. How would the dimensions change if the area was a different expression?
  2. Can you find the width and length of the rectangle if y=1y = 1?
  3. What happens to the dimensions if the length was defined differently, such as being 3 times the width?
  4. How can we graph the relationship between width and length for different values of yy?
  5. What are the properties of the quadratic formula that help us solve this problem?

Tip:

To solve a quadratic equation, always make sure to rearrange it in the standard form ax2+bx+c=0ax^2 + bx + c = 0 and then use the quadratic formula or factorization for solutions.

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Math Problem Analysis

Mathematical Concepts

Algebra
Quadratic Equations
Geometry

Formulas

Area of a rectangle A = l × w
Quadratic equation formula w = (-b ± √(b² - 4ac)) / 2a

Theorems

Quadratic formula

Suitable Grade Level

Grades 8-10