If x = b + c, y = c - a, z = a - b, then find the value of x2 + y2 + z2 - 2xy - 2xz + 2yz.

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RRB Group D 27 Sept 2022 Shift 3 Official Paper
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  1. 2b
  2. 4c2
  3. 4b2
  4. 4a2

Answer (Detailed Solution Below)

Option 3 : 4b2
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Detailed Solution

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Given: 

x = b + c, y = c - a, z = a - b

Formula used:

x2 + y2 + z2 - 2xy - 2xz + 2yz. = (-x + y + z)2

Calculation:

Lets put the values of x, y, z in above equation,

=> (-x + y + z)2 = (-(b+c) + (c-a) + (a-b))2

=> (-b - c + c -a + a - b)2

=> (-2b)2

=> 4b2

Hence, the correct answer is '4b2'.
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