Three students were given the expression shown and were asked to take a common factor out of two of the terms.
4-9x+21

Answer:
Step-by-step explanation:
Expression given → 4 - 9x + 21
Chang's expression → 4 - 3(3x + 7)
Chang's expression is incorrect because the correct expression is [4 - 3(3x - 7)]
Benjamin's expression → 4 + 3(3x + 7)
Benjamin's expression is incorrect because the correct expression is [4 - 3(3x - 7)]
Habib's expression → 4 + 12x
Habib's expression is incorrect because the correct expression is [4 - 3(3x - 7)]
Correct expression → [4 - 3(3x - 7)]