JoeyyTheWerido
contestada

On a recent exam, a student was asked to simplify the expression:

12(8x − 4y) − 3(12y + 9x)

Their work is shown below:
Step 1: 12(8x − 4y) − 3(12y + 9x)
Step 2: 96x − 48y − 36y + 27x
Step 3: 96x + 27x − 48y − 36y
Step 4: (96x + 27x) + (−48y − 36y)
Step 5: 123x − 84y

Part A: In which step did they make a mistake, and what was it? (2 points)

Part B: How would you correct the mistake and solve the problem? Show all of your work. (2 points)

Respuesta :

FireDragonz324

Part A: The mistake was made in Step 2 where the student combined like terms incorrectly. Instead of adding the terms 96x and 27x correctly, they mistakenly subtracted the coefficients of x terms.  

Part B: Step 2 Correction: 12(8x − 4y) − 3(12y + 9x) 96x − 48y − 36y − 27x (Correcting the mistake) Combine like terms: 96x - 27x - 48y - 36y 69x - 84y


Therefore, the corrected simplified expression is 69x - 84y. The mistake was corrected by correctly combining like terms for x and y separately.


Hope this helps! Pls mark me Brainliest! :P

fieryanswererft

Answer:

Part A: The student made mistake in 2nd step when multiplying -3 with 9x equals to -27x; not +27x.

Part B: Give minus sign infront of 27x and start solving the rest of the work

Correct Steps:

first step: 12(8x − 4y) − 3(12y + 9x)

second step: 96x - 48x - 36y - 27x  ← mistake was made only in this line

third step: 96x - 27x − 48y − 36y

fourth step: (96x -27x) + (-48y - 36y)

fifth step: 69x -84y

The answer should comes as 69x -84y.

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