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Mathematics 7 Online
OpenStudy (anonymous):

Could you please help me with question? @mathmate @dumbcow @SolomonZelman

OpenStudy (mathmate):

To help you get your answer faster, I suggest you post your question before tagging for help! :)

OpenStudy (anonymous):

I think it's Statement 6. @mathmate Sorry, usually everyone takes forever to come.

OpenStudy (anonymous):

These are the answer choices: A. Statement 4 B. Statement 5 C. State... 6 D. Statem.. 7

OpenStudy (mathmate):

They ask which is the \(first\) incorrect statement. This type of question is best answered by examining each statement in order, and be convinced that each one you looked at is correct before moving to the next one. This is a very good training in mathematical reasoning, so do not miss the chance of practice. If you tell me statement 6 is incorrect, you need to tell me first that statements 1,2,3,4,5 are ALL correct. Are you ready to make that claim?

OpenStudy (anonymous):

I don't know how to explain it, I know figure B has 2x's and 2y's shaded,figure = x^2 +y^2 + 2xy so I choose statement 6. @mathmate However, I did ask for help because I don't really understand too much of this problem.

OpenStudy (mathmate):

To do it properly, as I explained above, you need to Start with statement 1. Is statement 1 correct, and why?

OpenStudy (anonymous):

There are four triangles shaded and divided by halves, 2 triangles on the x side and 2 on the y side, which results in 2xy. Yes, it is correct.

OpenStudy (mathmate):

Very good! Especially the explanation. Now can you proceed the same way with statement 2?

OpenStudy (anonymous):

Aww, thanks! I'm trying to figure 2 out, but I'm not too sure. 4 half triangles are equivalent to c^2 ?

OpenStudy (mathmate):

Yes, you could say the white square has side =c, so area is c^2, Or, along the lines of your argument, there are 4 isosceles right triangles with hypotenuse c, so each leg is sqrt(c)/2, total area = 4((sqrt(c)/2)^2)=c^2. Good, can you proceed to statement 3?

OpenStudy (anonymous):

Statement 3 sums up the end result of both Statement 1 and 2, in Statement 1 I've proved 2xy is the end result and as stated above in statement 2- we concluded figure A= c^2. In order to find the area of figure A, you would add both of these which combines the end result of Statement 1 and 2 .

OpenStudy (mathmate):

Absolutely correct! You can now continue with statement 4.

OpenStudy (anonymous):

Therefore, we would add c^2 and 2xy= area. Statement 4: there are 4 squares which are divided by both x and y. 4 / 1/2 = 2 and if you include the variables it's 2xy (I'm not sure how much sense that mad.. )

OpenStudy (anonymous):

that made*

OpenStudy (mathmate):

Not exactly. The four grey triangles together have the same area as the two grey rectangles. Each grey rectangle has an area of a\(\times\)b, or x\(\times\)y or xy. So two rectangles together have an area of 2xy, so the statement is still correct. You follow so far?

OpenStudy (anonymous):

YEs.

OpenStudy (mathmate):

Now let's move on to #5. If you find #5 valid, then your proposed answer of #6 is correct (i.e. #6 is not valid). If #5 is not valid, then your answer should be #5 (first invalid statement) You follow the logic?

OpenStudy (mathmate):

@lilia222

OpenStudy (calculusfunctions):

It seems like enough people are helping you so I will just quickly add that Area of a shaded region = Area of the entire (outer) region - Area of each unshaded region.

OpenStudy (anonymous):

Area of side square= side ^2 , therefore, statement 5 is incorrect ..

OpenStudy (mathmate):

Can you tell me what should be the area of the white squares in B?

OpenStudy (mathmate):

@lilia222 I have to go now. As I said earlier, if you find the sum of the two white squares not equal to 2(x^2+y^2), then your answer would be #5 (i.e. first incorrect answer).

OpenStudy (anonymous):

So it is statement 5?

OpenStudy (mathmate):

Yes, it is, because it is the first invalid statement, as requested in the question. Well done! :)

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