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Maths year 11

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Divide the shape in two rectangles, find their respective areas and add them together.
Reply 703
Original post by RDKGames
Divide the shape in two rectangles, find their respective areas and add them together.


Like this ?

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Reply 704
Original post by RDKGames
Divide the shape in two rectangles, find their respective areas and add them together.


Like this ? .

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First equation is fine but if you're going by that then your second one is incorrect. Think about the line length 7x-2 in relation to the 2x at the top.


Split the diagram into 2 rectangles, and label all of the side lengths of each rectangle and it should become very clear.
Reply 708
Original post by RDKGames
First equation is fine but if you're going by that then your second one is incorrect. Think about the line length 7x-2 in relation to the 2x at the top.


Here


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Reply 709
I think it's 5x-2

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Original post by z_o_e
I think it's 5x-2

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The top length would indeed be 5x-2. Not sure why you multiplied (x+3) by itself there though.
Reply 711
Original post by RDKGames
The top length would indeed be 5x-2. Not sure why you multiplied (x+3) by itself there though.


How do I solve the last 2?


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Original post by z_o_e
How do I solve the last 2?


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That's not quite right. I think you would find it easier to expand brackets using a table; do you know how?
Reply 713
Original post by RDKGames
That's not quite right. I think you would find it easier to expand brackets using a table; do you know how?


No?

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Create a table like this. Since you are multiplying (x+3) by (5x-3), one goes on the top and the other goes on the side. The trick is that you separate the numbers by isolating them in their own squares; like 5x and -2 have different squares, likewise with x+3. Then fill it in by multiplying the corresponding column and row. For example, 5x2 is achieved from x multiplied by 5x . -2x is from -2 times by x.

Once you fill them in, add them all up and you have your brackets expanded.

ImageUploadedByStudent Room1470502924.674861.jpg


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(edited 7 years ago)
Reply 715
Original post by RDKGames
Create a table like this. Since you are multiplying (x+3) by (5x-3), one goes on the top and the other goes on the side. The trick is that you separate the numbers by isolating them in their own squares; like 5x and -2 have different squares, likewise with x+3. Then fill it in by multiplying the corresponding column and row. For example, 5x2 is achieved from x multiplied by 5x . -2x is from -2 times by x.

Once you fill them in, add them all up and you have your brackets expanded.

ImageUploadedByStudent Room1470502924.674861.jpg


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Thank you xx



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Not quite. Top row is incorrect because x term on the 5 is SQUARED while the one on the -2 is NOT. Therefore you cannot take one away from the other like that.

Second row, you are missing an x next to the 15.
Reply 717
Original post by RDKGames
Not quite. Top row is incorrect because x term on the 5 is SQUARED while the one on the -2 is NOT. Therefore you cannot take one away from the other like that.

Second row, you are missing an x next to the 15.


Oh is it 3x cube?

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Original post by z_o_e
Oh is it 3x cube?

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No it's simply 5x2-2x.

It would be 3x2 if it was 5x2-2x2.
It would be 3x3 if it was 5x3-2x3.
They powers have to be the same in order to mix.
Reply 719
image.jpg
Original post by B_9710
That's what I was asking for, the proof.

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