If (x + y) = 1,  then the value of      

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 Multiple Choice QuestionsMultiple Choice Questions

231.

If x + y + z = 6  and x2 + y2 + z2 = 20,  then the value of x3 + y3 + z3 - 3xyz is

  • 64

  • 70

  • 72

  • 76

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232.

If (x + y) = 1,  then the value of 
                  fraction numerator 1 over denominator straight x cubed straight y cubed end fraction space minus space straight x cubed space minus space straight y cubed is

  • 3

  • -3

  • 1

  • -1


A.

3

x.y (x + y) = 1
On cubing both sides,
                      [x. y (x + y)3] = (1)3
      x3. y3 [x3 + y3 + 3xy (x + y)] = 1
               straight x cubed space plus space straight y cubed space plus space 3 xy space left parenthesis straight x space plus space straight y right parenthesis space equals space fraction numerator 1 over denominator straight x cubed straight y cubed end fraction
          3 xy left parenthesis straight x space plus space straight y right parenthesis space equals space fraction numerator 1 over denominator straight x cubed straight y cubed end fraction space minus space straight x cubed space minus space straight y cubed
   Given,    x. y(x + y) = 1
therefore space space space 3 space cross times space 1 space equals space fraction numerator 1 over denominator straight x cubed straight y cubed end fraction minus straight x cubed space minus space straight y cubed
space equals space space fraction numerator 1 over denominator straight x cubed straight y cubed end fraction space minus space straight x cubed space minus space straight y cubed space equals space 3

                 
           

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233.

If a + b + c = 2s, then
    fraction numerator left parenthesis straight s minus straight a right parenthesis squared space plus space left parenthesis straight s minus straight b right parenthesis squared space plus space left parenthesis straight s minus straight c right parenthesis squared space plus space straight s squared over denominator straight a squared space plus space straight b squared space plus space straight c squared end fraction is equal to

  • a2 + b2 + c2

  • 0

  • 1

  • 2

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234.

If straight a space plus space fraction numerator 1 over denominator straight a minus 2 end fraction space equals space 4 comma then the value of

  • 0

  • 2

  • -2

  • 4

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235.

If a3 - b3 - c3 = 0,  then the value of a9 - b9 - c9 - 3a3b3c3 is

  • 1

  • 2

  • 0

  • -1

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236.

If x = 332,  y = 333,   z = 335,  then the value of x3 + y3 + z3 - 3xyz is

  • 10000

  • 7000

  • 9000

  • 8000


237.

If m = -4,  n = -2, then the value of 
m3 - 3m2 + 3m + 3n + 3n2 + n3

  • -126

  • 124

  • 126

  • -124


238.

The value of fraction numerator 1 over denominator square root of 7 minus square root of 6 end fraction space minus space fraction numerator 1 over denominator square root of 6 begin display style minus end style begin display style square root of 5 end style end fraction plus fraction numerator 1 over denominator square root of 5 begin display style minus end style begin display style 2 end style end fraction minus fraction numerator 1 over denominator square root of 8 begin display style minus end style begin display style square root of 7 end style end fraction plus fraction numerator 1 over denominator 3 minus square root of 8 end fraction

  • 5

  • 1

  • 0

  • 7


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239.

If straight x space equals space fraction numerator 2 plus square root of 3 over denominator 2 minus square root of 3 end fraction space comma then the value of straight x space plus space 1 over straight x ?

  • 14

  • 8 square root of 3

  • 0

  • 18


240.

If straight x space equals space 2 space plus space square root of 3 comma space then what is the value of square root of 2 straight x space plus space fraction numerator 1 over denominator square root of 2 straight x end root end fraction ?

  • 2 square root of 3

  • 3 square root of 3

  • fraction numerator left parenthesis 3 square root of 3 space plus space 1 right parenthesis over denominator 2 end fraction

  • 2 square root of 3 space plus space 1


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