Solve the Quadratic equation by completing the square. x^2+14x+48=0

Question

Having trouble with completing the square problems 

Answer 1

You must memorize the process.  When you have a quadratic equation like x² + 14x + 48 = 0, do this:

 

1.  move the constant 48 to the opposite side and give it the opposite sign that it had while on left side (equivalent to subtraction)

 

2.  Take half of the coefficient of the x-only term: this gives 7

 

3.  Square that!  Now you have 49; add it to each side, giving

   x² + 14x + 49 = 49 -48

 

4. When this is done, the left side of the equation IS GUARANTEED TO BE A PERFECT SQUARE:

   (X + 7)² = 1

 

5.  TAKE SQUARE ROOT OF EACH SIDE, AND REMEMBER TO PUT ± IN FRONT OF THE RIGHT SIDE:

   (X + 7) = ±1

 

6.  Evaluate x;  x = -7 -1 or -7 + 1, that is, x = {-8, -6)