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Akanki agrawal

· started a discussion

· 1 Months ago

Wrong answer & no detailed solution (Question: 336999.0 )

Can u prove, how it is 7y^2 & not 6y^2?

Plz check it again.

Question:

 If a = x + y, b = x – y, c = x + 2y, then the value of a2 + b2 + c2 – ab – bc – ca  is – 

Options:
A)

4y2

B)

7y2

C)

6y2

D)

5y2

Solution:

Ans: (b) 


Knowledge Expert

· commented

· 1 Months ago

Dear Student,

Detailed solution already given, go to report and click on show button.
in this question Formula of (a + b + c)2 = a^2 + b^2 + c^2 + 2ab + 2bc + 2ca
but in question given (a + b + c)2 = a^2 + b^2 + c^2 -ab - bc - ca so we can't apply this formula directly.
according to question
we find the value of a-b, b-c, c-a. and put the value in given equation see in the solution after simplify the equation we get 1/2{(2y)^2+ (-3y)^2+ (y)^2}
1/2 (4y^2+ 9y^2 +y^2)
1/2(14y^2)= 7y^2
please read the solution carefully and try again.

Keep learning keep solving
Best wishes
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