Maths-
SAT
Easy

Question

x plus 1 equals fraction numerator 2 over denominator x plus 1 end fraction
In the equation above, which of the following is a possible value of x + 1 ?

  1. 1 minus square root of 2
  2. square root of 2
  3. 2
  4. 4

The correct answer is: square root of 2


    Given x plus 1 equals fraction numerator 2 over denominator x plus 1 end fraction
    (x + 1)(x +1) = 2
    x2 + x + x + 1 = 2
    x2 + 2x + 1 = 2
    x2 + 2x + 1 – 2 = 0
    x2 + 2x – 1 = 0
    The above Quadratic equation cannot be factorized. Thus, quadratic formula can be applied.
    x equals fraction numerator open square brackets negative b plus-or-minus square root of b squared minus 4 a c end root close square brackets over denominator 2 a end fraction
    a = 1
    b = 2
    c = -1
    x equals fraction numerator open parentheses negative 2 plus-or-minus square root of 2 squared minus 4 left parenthesis 1 right parenthesis left parenthesis negative 1 right parenthesis end root close parentheses over denominator 2 left parenthesis 1 right parenthesis end fraction
    fraction numerator negative 2 plus-or-minus square root of 4 plus 4 end root over denominator 2 end fraction
    fraction numerator negative 2 plus-or-minus square root of 8 over denominator 2 end fraction
    square root of 8 equals square root of 4 cross times 2 end root equals 2 square root of 2
    x equals fraction numerator negative 2 plus-or-minus 2 square root of 2 over denominator 2 end fraction
    x equals negative 1 plus-or-minus square root of 2
    x equals negative 1 plus square root of 2 text  and  end text x equals negative 1 minus square root of 2
    x equals negative 1 plus square root of 2
    x plus 1 equals negative 1 plus square root of 2 plus 1 equals square root of 2

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