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Question

The roots of the equation $9(x+9)^2=441$ are:

This question was previously asked in
RRB NTPC 2019 CBT 1 Question Paper (8-Mar-2021) (Shift 2)
The correct answer is
-2, -16

Solving the Equation $9(x+9)^2=441$

To find the roots of the given equation, we first isolate the squared term:

  1. Divide both sides by 9:

    $ (x+9)^2 = \frac{441}{9} $

    $ (x+9)^2 = 49 $

  2. Take the square root of both sides. Remember to include both positive and negative roots:

    $ x+9 = \pm\sqrt{49} $

    $ x+9 = \pm 7 $

  3. Solve for x in both cases:

    • Case 1 (Positive root):

      $ x + 9 = 7 $

      $ x = 7 - 9 $

      $ x = -2 $

    • Case 2 (Negative root):

      $ x + 9 = -7 $

      $ x = -7 - 9 $

      $ x = -16 $

Therefore, the roots of the equation $9(x+9)^2=441$ are -2 and -16.

Verification

The roots found are -2 and -16, which corresponds to Option D.

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Important Questions from Quadratic Equation

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