Question

Erica solved the equation −5x − 25 = 78; her work is shown below. Identify the error and where it was made. (5 points)

−5x − 25 = 78
Step 1: −5x − 25 − 25 = 78 − 25
Step 2: −5x = 53
Step 3: = -5x/-5=53/-5
Step 4: x = -53/5

Answer 1

−5x − 25 = 78

Step 1: −5x − 25 − 25 = 78 − 25 WRONG

- 5x - 25 = 78

- 5x - 25 + 25 = 78 + 25

- 5x = 103

x = - 103/5

x = - 20,6

Answer 2

Explanation:

−5x − 25 = 78

Step 1: −5x − 25 − 25 = 78 − 25 <== this is where the error was made.

Step 2: −5x = 53

Step 3: = −5x/−5=53/−5

Step 4: x = −53/5

Right steps:

−5x − 25 = 78

Step 1: −5x − 25 + 25 = 78 + 25

Step 2: −5x = 103

Step 3: −5x/−5 = 103/−5

Step 4: x = 103

Step 1 was where the error was, because she subtracted 15 from both sides instead of adding 15, so they cancelled out.

Hope this helps!