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Buster
Lv 6
Buster asked in Science & MathematicsMathematics · 10 years ago

Need some help with two algebra questions?

1. A 25 foot ladder is leaning against a house. If the bottom of the ladder is 15ft from the base of the house, how high does the ladder reach?

2. The width of a rectangle is 3m less than the width. The area of the rectangle is 18n^2. Find the lenghth and the width.

Please show me how to solve for both of these. Thank you.

2 Answers

Relevance
  • 10 years ago
    Favorite Answer

    √(15² + x²) = 25

    225 + x² = 625

    x² = 400

    x = 20

    Answer 1: 20 feet

    --------------

    Length—x:

    x(x - 3) = 18

    x² - 3x = 18

    x² - 1.5x = 18 + (- 1.5)²

    x² - 1.5x = 18 + 2.25

    (x - 1.5)² = 20.25

    x - 1.5 = 4.5

    x = 6

    Width:

    = 6 - 3

    = 3

    Answer: length, 6 feet; width, 3 feet

  • Bob B
    Lv 7
    10 years ago

    The 25-foot ladder is the hypotenuse of a right triangle with 15 feet as one side and the height as the other. The formula for a right triangle is:

    c^2 = a^2 + b^2 where c is the hypotenuse with a and b as the sides

    25^2 = 15*2 + b^2

    625 = 225 + b^2

    Subtract 225 from both sides:

    400 = b^2

    b = sqrt(400) = 20 feet

    2. The width of a rectangle is 3m less than the width. The area of the rectangle is 18n^2. Find the lenghth and the width.

    Use these two equations:

    L = W + 3 [width plus 3 meters equals the length]

    L * W = 18 [area, length times width, is 18]

    Substitute (W + 3) [from equation 1] for L in equation 2:

    (W + 3) * W = 18

    Multiply out the left side:

    W^2 + 3W = 18

    Rewrite to quadratic form:

    W^2 + 3W - 18 = 0

    Factor to:

    (W + 6)(W - 3) = 0

    Ignore the negative root (width must be positive).

    The width is 3 meters and the length (W + 3) is 6 meters.

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