help needed! Quadratic equation
- Thread starter Pexius
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AvgStudent
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What do you mean by "solving for h"?
Do you mean you want to isolate h or do you want to find the roots of the quadratic?
D
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Your equation is:
1.44*h2 - 2.4*h + A = 0 ..................................(1)
The standard quadratic equation:
a*x2 + b*x + c = 0 ..................................................................(2) ........................................do you know the solution to equation (2)?
Unsure, the question asks to show that the area of 'A' can be expressed in terms of h by the quadratic equation
yes, i calculated it as 1.44 x 1.662 + 2.4 x 1.66 + A = 0
it's just not clicking in my brain
AvgStudent
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I don't think you posted the entire problem. Where did 1.66 come from?
apologies, i used the formula x = -b/2a to obtain the value for x, then substituted that into the y = ax2+bx+c
AvgStudent
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Ok, by using that equation you found the vertex of the parabola. I got a different answer, you might wanna check for "a" and "b" again.
Anyhow, I'm still unsure what QUESTION you're trying to answer. Can you post a picture of the problem?
AvgStudent
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I notice that this is part ii). I'm guessing the information from the problem statement and part i) are needed to answer ii).
Can you show that as well? Note that the question is not asking for you to solve for h, but to show how they came up with the equation for A, the area.
Do you see that both part i and part ii depend on information given before them, which we do not have.
This ii why, in our guidelines, we ask that you post the complete problem. Often the issue is that the student misses a relevant piece of information. Because the student is not aware that the information is relevant, the student does not include it in a summary of the problem. It is much quicker if the complete problem is given up front.
Please do so. Then we can help.
This ii why, in our guidelines, we ask that you post the complete problem. Often the issue is that the student misses a relevant piece of information. Because the student is not aware that the information is relevant, the student does not include it in a summary of the problem. It is much quicker if the complete problem is given up front.
Please do so. Then we can help.
roger that, first time consulting a forum for help. still learning...
AvgStudent
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Are you planning to provide all of the information given?
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AvgStudent
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Great now we have all of the information needed to answer the questions.
Start with part i)
If you read the question carefully, it's not asking you to solve anything. It wants you to show that the width is [imath]w=2-1.2h[/imath] given the perimeter is 4 meters. Can you write the formula for the perimeter of a rectangle i.e. the window?
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Felt comfortable with this question, part 2 is what frustrates me. Probably a case of over thinking but hoping for some clarity from someone who understands it better than me
AvgStudent
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Nice, but it's also asking you to explain each step.
Part ii) is a similar idea but starts with the formula for the area of a rectangle.
Thank you for providing the complete problem.
Let’s see if this helps. A is the total area. But it is the sum of three areas.
[math]A = A_1 + A_2 + A_3 = \left ( h * \dfrac{w}{2} \right ) + \left ( h * \dfrac{w}{2} \right ) + ( 0.2h * w ) =\\ hw * \left ( \dfrac{1}{2} + \dfrac{1}{2} + 0.2 \right ) = 1.2hw.[/math]
Do you follow that?
Now actually there was an error in your solution to part i.
[math]4 = (h + 0.2h) + w + (h + 0.2h) + w = 2h + 2 * 0.2h + 2w = 2.4h + 2w \implies\\ 2w = 4 - 2.4h \implies w = 2 - 1.2h \ne 0.8.[/math]
Do you see where your error occurred?
If so, can you now do part ii?
Let’s see if this helps. A is the total area. But it is the sum of three areas.
[math]A = A_1 + A_2 + A_3 = \left ( h * \dfrac{w}{2} \right ) + \left ( h * \dfrac{w}{2} \right ) + ( 0.2h * w ) =\\ hw * \left ( \dfrac{1}{2} + \dfrac{1}{2} + 0.2 \right ) = 1.2hw.[/math]
Do you follow that?
Now actually there was an error in your solution to part i.
[math]4 = (h + 0.2h) + w + (h + 0.2h) + w = 2h + 2 * 0.2h + 2w = 2.4h + 2w \implies\\ 2w = 4 - 2.4h \implies w = 2 - 1.2h \ne 0.8.[/math]
Do you see where your error occurred?
If so, can you now do part ii?
thankyou for the clarification. is much appreciated.