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
I think it is Step 1

Answer 1

@Phebe @Data_LG2 can you help? sorry to bother

Answer 2

no worries, we're here to help.

The student is trying to do the elimination method. Why do you think it is the Step 1?
Multiplying the 1st equation by a number in order to eliminate m is right. Check it again.
Think of it this way, how will you do it (solve the equation using elimination method) if the student is you? Try solving it your own first, then compare it to the solution of the student.

Answer 3

@Data_LG2 for n i got -10 i thought it was step 1 because the 3( m) was a negative but it did tn switch sides ( im not very good with the other properties such as elimination and substitution so bear with me please)

Answer 4

:) ok

how did you get n = -10? maybe we can work on your solution

Answer 5

I'm not very good at explaining it :/ like i know how i got it but im not good with words and writing it out... Could you perhaps write out like basic steps and i can compare it. (ex. multiply this equation with that) Sorry i know i sound kinda stupid but im probably gonna try to explain and than say something that isnt how i worked it out..

Answer 6

Okay so i know the steps now

Step 1: Arrange both equations so the corresponding variables are above one another. You may need to rewrite one of the equations to do this.
Step 2: Look for variables that have opposite coefficients (+/–) or coefficients that are multiples (such as 2 and 4, and so on).
Step 3: If needed, multiply one equation to create coefficients that add to zero (or cancel when added).
Step 4: Add both equations, eliminating one variable.
Step 5: Solve for the remaining variable.
Step 6: Substitute the value you found in Step 5 into one of the original equations. Solve for the second variable. You now have a solution that can be written as an ordered pair, such as (x, y).
Step 7: Check your work using substitution to verify that the solution works in both equations.
Right?

Answer 7

okay sure, no problemo :)

Yes those steps are absolutely right

Apply Elimination method in your question:
1. Multiply both sides by -3 (because when you add the eqns together, variable m will be eliminated).
2. Then simplify it then add those two together.
3. Check carefully on how the student add the two equations(is the student missing something)

Answer 8

@Data_LG2 so the student made an error on step 3 OHHHHH okay i get it now. Can you hlep me with one more please and thats it

Answer 9

do you know what the error in step 3 is?

Answer 10

( sorry im multi tasking rn) I think the equations are written wrong. Wait where did that 34 some from is that part of the erorr to?

Answer 11

34? O.o

Answer 12

24*

Answer 13

(again multi tasking)

Answer 14

lol okay...

hmm what do you mean by " equations are written wrong"

Answer 15

Well for one the 24 shouldnt be there and shouldnt there be a 4 in it