SOLUTION: in completing the square for the following problem, Jules and Vincent are trying to find their error as they are disagreeing on the answer. Describe the error(s) made in the proces

Algebra ->  Radicals -> SOLUTION: in completing the square for the following problem, Jules and Vincent are trying to find their error as they are disagreeing on the answer. Describe the error(s) made in the proces      Log On


   

Question 1089760: in completing the square for the following problem, Jules and Vincent are trying to find their error as they are disagreeing on the answer. Describe the error(s) made in the process and solve the problem correctly. Upload your solution for your instructor to grade.
step 1: x^2+8x=0
step 2: x^2+8x+8=0+8
step 3: (x+4)^2=8
step 4: x+4=2\sqrt{2}
step 5: x=-4=-2\sqrt{2}
Found 2 solutions by MathLover1, ikleyn:
Answer by MathLover1(20850) About Me  (Show Source):
You can put this solution on YOUR website!

step 1: x%5E2%2B8x=0
step 2: x%5E2%2B8x%2B8=0%2B8-> here is error;Jules and Vincent added 8, but they needed to add 16 or 4%5E2 because coefficient 2ab=8; since +a=1->2b=8->b=8%2F2->b=4, then we add b%5E2 or 4%5E2 and we get x%5E2%2B8x%2B4%5E2=0%2B4%5E2->x%5E2%2B8x%2B16=16
step 3: %28x%2B4%29%5E2=8...should be %28x%2B4%29%5E2=16
step 4: x%2B4=2sqrt%282%29...should be %28x%2B4%29=sqrt%2816%29->%28x%2B4%29=4 or %28x%2B4%29=-4
step 5: x=-4=-2\sqrt{2}....x=4-4->x=0 or x=-4-4->x=-8

Answer by ikleyn(52806) About Me  (Show Source):
You can put this solution on YOUR website!
.
in completing the square for the following problem, Jules and Vincent are trying to find their error as they are disagreeing
on the answer. Describe the error(s) made in the process and solve the problem correctly. 

step 1: x^2+8x=0            Correct.            x^2 + 8x = 0

step 2: x^2+8x+8=0+8        Incorrect. Must be  x^2 + 8x + 16 = 0 + 16.

step 3: (x+4)^2=8           Incorrect. Must be  (x+4)^2 = 16.

step 4: x+4=2\sqrt{2}       Incorrect. Must be  x + 4 = +/- 4.

step 5: x=-4=-2\sqrt{2}     Incorrect. The answer is: x = 0  or  x = -8.

On completing the squares to solve quadratic equations see the lesson
    - HOW TO solve quadratic equation by completing the square - Learning by examples
in this site.


Also,  you have this free of charge online textbook in ALGEBRA-I in this site
    - ALGEBRA-I - YOUR ONLINE TEXTBOOK.

The referred lesson is the part of this online textbook under the topic  "Quadratic equations".


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