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# Area triangle, showing it can be represented by given equation watch

1. The diagram of the triangle can be seen on the past paper in this link, it's question 10i:

http://www.mei.org.uk/files/papers/c107ju_6gfd3.pdf

The triangle's base length is 2x - 3 and its perpendicular height is x + 1, it's area is 9cm^2, show that 2x^2 - x - 21 = 0

I got this so far:
1/2(base x height)
1/2(2x-3)(x+1) = 9
1/2(2x^2 + 2x -3x -3) = 9
1/2(2x^2 - x -3) = 9
I can already see, I'm not going to get the right answer, the markscheme says you multiply the 9 by 2, but why?
2. Everything you've done is right, what the markscheme is doing is multiplying both sides by 2 so as to get rid of the half on the left hand side. With a simple rearrange you then have the right answer.
3. (Original post by Magenta96)
The diagram of the triangle can be seen on the past paper in this link, it's question 10i:

http://www.mei.org.uk/files/papers/c107ju_6gfd3.pdf

The triangle's base length is 2x - 3 and its perpendicular height is x + 1, it's area is 9cm^2, show that 2x^2 - x - 21 = 0

I got this so far:
1/2(base x height)
1/2(2x-3)(x+1) = 9
1/2(2x^2 + 2x -3x -3) = 9
1/2(2x^2 - x -3) = 9
I can already see, I'm not going to get the right answer, the markscheme you muliply the 9 by 2, but why?
9/0.5 = 9x2
4. (Original post by Magenta96)
The diagram of the triangle can be seen on the past paper in this link, it's question 10i:

http://www.mei.org.uk/files/papers/c107ju_6gfd3.pdf

The triangle's base length is 2x - 3 and its perpendicular height is x + 1, it's area is 9cm^2, show that 2x^2 - x - 21 = 0

I got this so far:
1/2(base x height)
1/2(2x-3)(x+1) = 9
1/2(2x^2 + 2x -3x -3) = 9
1/2(2x^2 - x -3) = 9
I can already see, I'm not going to get the right answer, the markscheme you muliply the 9 by 2, but why?
How else would you suggest getting rid of the 1/2
5. (Original post by Magenta96)
The diagram of the triangle can be seen on the past paper in this link, it's question 10i:

http://www.mei.org.uk/files/papers/c107ju_6gfd3.pdf

The triangle's base length is 2x - 3 and its perpendicular height is x + 1, it's area is 9cm^2, show that 2x^2 - x - 21 = 0

I got this so far:
1/2(base x height)
1/2(2x-3)(x+1) = 9
1/2(2x^2 + 2x -3x -3) = 9
1/2(2x^2 - x -3) = 9
I can already see, I'm not going to get the right answer, the markscheme you muliply the 9 by 2, but why?
I think it is a mistake to think your answer is wrong when you have used a different method to the examiner.

Some marks scheme actually show several possible solutions to a problem. If I did a question today by a particular method I might well do it a different way next week. It's rather like a car journey - often several acceptable routes and you don't necessarily know in advance which is the best route/solution.
6. I understand now, thank you everyone

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