Question

Terry solved the system of equations below. What mistake did he make in his work?
3x + y = 6
x − 2y = 2

y = 6 − 3x
x − 2(6 − 3x) = 2
x − 12 − 6x = 2
−5x − 12 = 2
+12 +12
-----------------
-5x/-5=14/-5
x = −2.8

3(−2.8) + y = 6
−8.4 + y = 6
+8.4 +8.4
---------------
y = 14.4

A. He should have substituted 6 + 3x.

B. He combined like terms incorrectly. It should have been 5x instead of −5x.

C. He made a mistake in distributing −2.

D. He made no mistake.

Answer 1

Great question. What do you think?

Answer 2

Walk me through your thought process

Answer 3

did he make any mistakes ?

Answer 4

Yes he made a mistake.

Answer 5

what is it

Answer 6

Look real close at the 4th equation and what he did in the fifth equation. It was not a correct transition.

Answer 7

He combined like terms incorrectly. It should have been 5x instead of −5x.

Answer 8

x − 2(6 − 3x) = 2
x − 12 − 6x = 2

Do you see the error above?

Answer 9

What he did was incorrectly distribute the -2

Answer 10

oh he made a mistake in distributing −2.

Answer 11

He goofed on the sign it should be +6x not -6x

Answer 12

Do you see it now?

Answer 13

oh

Answer 14

yes i do

Answer 15

Yes in distributing the -2 he messed up on the sign on one of the terms. That is easy to do, I have made the same mistake many times.

Answer 16

oh thanks

Answer 17

You're welcome, and remember to keep track of those signs lol.

Answer 18

yeah ok