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anonymous

  • 4 years ago

The length of a rectangle is 2m more than the width. The area of the rectangle is 20 m^2. Find the dimensions of the rectangle, to the nearest tenth of a metre.

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  1. anonymous
    • 4 years ago
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    The answer is 3.6 m by 5.6m... how?

  2. anonymous
    • 4 years ago
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    We know that for a rectangle, the area is length x width A = l*w We know that the length is 2 meters more than the width So the the length minus 2 in the width => l - 2 = w l = w + 2 Substitutin in the area formula: A = (w+2)(w) 20 = w(w+2) Solve for w using the quadratic equation, then using the w you can find l

  3. anonymous
    • 4 years ago
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    solve for w using the quadratic equation? so it's going ot be w^2 + 2w - 20 = 0

  4. anonymous
    • 4 years ago
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    yup

  5. anonymous
    • 4 years ago
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    ohhhh,

  6. anonymous
    • 4 years ago
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    Get it now? :)

  7. anonymous
    • 4 years ago
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    yup! Oh, but what's a product of -20 and a sum -20? o.o

  8. anonymous
    • 4 years ago
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    Product of -20, sum of 2... Do you know how to use the quadratic equation?

  9. anonymous
    • 4 years ago
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    sort of.. isn't it like factoring?

  10. anonymous
    • 4 years ago
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    Its like factoring, but when like integer numbers dont work to solve the equation http://www.oncalc.com/wp-content/uploads/2011/02/quadratic-equation-calculator.gif

  11. anonymous
    • 4 years ago
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    You see that equation before?

  12. anonymous
    • 4 years ago
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    ohhhh the quadratic formula?

  13. anonymous
    • 4 years ago
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    Yeah, sorry didnt know what you call it

  14. anonymous
    • 4 years ago
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    it's okay. But what about it? That's all I use after I've figured it's w^2 + 2w - 20 =0?

  15. anonymous
    • 4 years ago
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    Yup, plug it in to the quadratic formula

  16. anonymous
    • 4 years ago
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    ohh, thank you!

  17. anonymous
    • 4 years ago
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    Okay, well I got -2 +/- 2sqr.rt:21/2 ...

  18. anonymous
    • 4 years ago
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    punch that into a calculator and what do you get?

  19. anonymous
    • 4 years ago
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    so I don't have to do 2(-2 +/- sqr.rt:21/2?

  20. anonymous
    • 4 years ago
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    well what number do you get from that?

  21. anonymous
    • 4 years ago
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    Like evaluate the expression

  22. anonymous
    • 4 years ago
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    not the answer.

  23. anonymous
    • 4 years ago
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    (-2 + sqrt ( 4 - 4(1)(-20) )/ 2

  24. anonymous
    • 4 years ago
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    I got 3.58

  25. anonymous
    • 4 years ago
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    if you do (-2 - sqrt ( 4 - 4(1)(-20) )/ 2 , you get a negative number, and can omit it because there is no such thing as negaive lengths

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