Question

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

Equation 1: m = 8 + 2n
Equation 2: 3m = 4 + 4n



Step 1:
−3(m) = −3(8 + 2n) [Equation 1 is multiplied by −3.]
3m = 4 + 4n [Equation 2]

Step 2:
−3m = −24 − 6n [Equation 1 in Step 1 is simplified.]
3m = 4 + 4n [Equation 2]

Step 3:
−3m + 3m = −24 − 6n + 4n [Equations in Step 2 are added.]

Step 4:
0 = −24 − 2n

Step 5:
n = −12


In which step did the student first make an error?

Step 4

Step 3

Step 2

Step 1

Answer 1

I think the student first made an error on step 1 because why is it multiplied by -3. To be more precise, where did the student get the -3 from?

Answer 2

Step 3

Explanation:

Hello

the student made a mistake in the step number 3.

let´s see

in the step number 1 he multiplied by -3 in order to add this new equation with equiation 2 and then eliminate the terms with m

Step one

-3(m)=-3(8+2n)

-3m= -24 - 6 n, it is ok

in step two he simplified, he did it well.

in the step 3 he added the equations

-3m = -24-6n

3m = 4 +4n

_____________

0 = -20-2n

he did not add properly -24+4, here , he made his first mistake.

step 4 is already wrong

continuing..to find n

0= -20-2n

20=-2n

n=-10

Have a great day