The work of a student to solve the equation 2 (4x - 4) = 8 + 4x + 4 is shown below: Step 1. 2 (4x - 4) = 8 + 4x + 4 Step 2. 6x - 6 = 12 + 4x Step 3. 6x - 4x = 12 + 6 Step 4. 2x = 18 Step 5. x = 9 In which step did the student first make an error and what is the correct step? Step 2, 8x - 6 = 2 (6 + 2x + 2) Step 2, 8x - 8 = 12 + 4x Step 3, 6x - 4x = 12 - 6 Step 3, 6x + 4x = 12 + 6

Question

Mathematics

Pablo Mcclure

12 May, 16:05

The work of a student to solve the equation 2 (4x - 4) = 8 + 4x + 4 is shown below: Step 1. 2 (4x - 4) = 8 + 4x + 4 Step 2. 6x - 6 = 12 + 4x Step 3. 6x - 4x = 12 + 6 Step 4. 2x = 18 Step 5. x = 9 In which step did the student first make an error and what is the correct step? Step 2, 8x - 6 = 2 (6 + 2x + 2) Step 2, 8x - 8 = 12 + 4x Step 3, 6x - 4x = 12 - 6 Step 3, 6x + 4x = 12 + 6

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Answers (1)

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Jake Hudson · Answer 1

Answer is step 2, 8x - 8 = 12 + 4x

The student did not distribute the 2 into the parentheses properly which ruined their entire problem. With 2 (4x-4), you must multiply everything in parentheses by 2.

so 2 x 4x = 8x

2 x - 4 = - 8

making it 8x - 8 = 12 + 4x (on the right side all you did was combine like terms)