Maths-
General
Easy

Question

x to the power of 2 end exponent minus 14 x plus 40 equals 2 x plus 1
What is the sum of the solutions to the given equation?

  1. negative 16    
  2. negative 14    
  3. 14    
  4. 16    

The correct answer is: 16


    The given equation is a quadratic equation (i.e. Highest power of a variable is 2). We will solve the given quadratic equation and find the sum of the solutions so obtained.
    Step-by-step solution:-
    x2 - 14x + 40 = 2x + 1
    x2 - 14x - 2x + 40 - 1 = 0
    x2 - 16x +39 = 0 -------------------------- (equation i)
    Comparing equation i with the general form of a quadratic equation i.e. ax2 + bx + c = 0, we get-
    a = 1, b = -16, c = 39
    Using factorization method (we factorize a × c i.e. 1 × 39 i.e. 39 into 2 factors such that the addition of these 2 factors gives a value that is equal to b i.e. -16)-
    ∴ we factorize 39 into -3 and -13 (because -3 × -13 = 39 and -3 + (- 13) = -16)
    x2 - 13x - 3x +39 = 0
    ∴ x (x - 13) - 3 (x - 13) = 0------------- (Taking common factors)
    ∴ (x - 3) (x - 13) = 0
    ∴ either x - 3 = 0 or x - 13 = 0
    ∴ either x = 3 or x = 13
    ∴ the solutions of the given equation are 3 and 13
    Sum of the solutions = 3 + 13 = 16
    Final Answer:-
    Option D i.e. 16 is the correct Option.
    Note:-
    Alternatively, formula method to solve the quadratic equation can also be used to find the solution of equation i above. Formula-
    x equals fraction numerator negative b plus-or-minus square root of open parentheses b to the power of 2 end exponent minus 4 a c close parentheses end root over denominator 2 a end fraction

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