All Junior Cert Mathematics posts
  • avatar image

    QUADRATIC EQUATIONS HELP HELP Ckf2001

    Arthur wants to fence three sides of his rectangular garden. The fourth side of the garden faces into the back of his house. He has 80 metres of fencing. Let x represent the width of his garden and let y represent the length of his garden.

    i) show that y = 80-2x

    ii) write an expression for the area of the garden in terms of x

    iii) if the garden has an area of 487.5m^2 find two possible values for the width and length of the garden

    How would I answer these I'm so stuck

    1. avatar image

      roro123

      y is 80-2x as the 3 sides add up to 80. To get the length (y) you take away the width (x) times 2 as this are has 1 length and 2 widths.

    2. avatar image

      roro123

      (ii) area = x times y (width times length). width=x and length= 80-2x. therefor area is (x)(80-2x) which is 80x-2x^2.

    3. avatar image

      roro123

      (iii) 80x-2x^2=487.5 = -2x^2+80x-487.5=0. Solve this using the -b formula.

    4. avatar image

      roro123

      I think they are all right, sorry if they are wrong. I didn't write out how to finish (iii) as i can't type it!!

    5. avatar image

      Me

      Share files from your computer
      loader