Question

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

Equation 1: m = 8 + 2n
Equation 2: 4m = 4 + 4n


Step 1: −4(m) = −4(8 + 2n) [Equation 1 is multiplied by −4.]
4m = 4 + 4n [Equation 2]
Step 2: −4m = −32 − 8n [Equation 1 in Step 1 is simplified.]
4m = 4 + 4n [Equation 2]
Step 3: −4m + 4m = −32 − 8n + 4n [Equations in Step 2 are added.]
Step 4: 0 = −32 − 4n
Step 5: n = −8


In which step did the student first make an error?

Answer 1

step3

Explanation:

Answer 2

In step 3

4m = 4 + 4n

-4m = -32 -8n. (step 2)

If you add -4m, 4m you end up with

-4m+4m=-32 -8n + 4n +4

In step 3. the 4 was not added

continuing to solve 4n=-28, n=-7