Question

The work of a student to solve a set of equations is shown:

Equation A: y = 16 – 2z
Equation B: 7y = 2 – 4z


Step 1: –7(y) = –7(16 – 2z) [Equation A is multiplied by –7.]
7y = 2 – 4z [Equation B]
Step 2: –7y = 16 – 2z [Equation A in Step 1 is simplified.]
7y = 2 – 4z [Equation B]
Step 3: 0 = 18 – 6z [Equations in Step 2 are added.]
Step 4: 6z = 18
Step 5: z = 3


In which step did the student first make an error?

Answer 1

Error in step 2

Step 2: –7y = 16 – 2z [Equation A in Step 1 is simplified.]
(forgot to multiply -7 on the right side)

should be
Step 2: –7y = -112 + 14z [Equation A in Step 1 is simplified.]