Question

Find the Error A student is solving −2(x−5)=12-2(x-5)=12. Which of the following explains the student's mistake?

−2(x−5)=12

−2x−5=12

−2x−5+5=12+5

−2x=17

x=−8.5

The student should have divided by 2, not –2.
The student should have distributed and written –2x + 5, not –2x – 5.
The student added 5 to both sides of the equation instead of subtracting 5.
The student only distributed the –2 to the first term inside the parentheses instead of both terms.

Answer 1

The second option: The student should have distributed and written -2x+5, not -2x-5.

That’s because the two negatives make a positive when multiplying/distributing.