Question

Difficulty: MediumQuadratic Equations and Factoring

Which of the following values are solutions to the equation (x+4)2=49(x + 4)^2 = 49? Select all that apply.

  1. 11-11Answer
  2. B
    3-3
  3. 33Answer
  4. D
    77
  5. E
    33\sqrt{33}

Answer

The correct solutions are 11-11 and 33.
Taking the square root of both sides of (x+4)2=49(x + 4)^2 = 49 yields x+4=7x + 4 = 7 or x+4=7x + 4 = -7. Solving these two linear equations gives x=3x = 3 and x=11x = -11. Both values satisfy the original quadratic equation.

Step-by-Step Solution

1
Apply the square root property to both sides of the quadratic equation.
x+4=±49=±7x + 4 = \pm \sqrt{49} = \pm 7
Taking the square root of both sides accounts for both the positive and negative roots of 4949.
2
Solve the first linear equation for the positive case.
x+4=7    x=74=3x + 4 = 7 \implies x = 7 - 4 = 3
Subtract 44 from both sides when the expression equals +7+7.
3
Solve the second linear equation for the negative case.
x+4=7    x=74=11x + 4 = -7 \implies x = -7 - 4 = -11
Subtract 44 from both sides when the expression equals 7-7.

Key Concept

Square Root Property of Quadratic Equations
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