-2(x - 1) = -8 Can You Find the ERRORS in This Work? Basic Algebra - Common Mistakes!
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- เผยแพร่เมื่อ 11 ก.ย. 2024
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I dont know why you have to distribute anything ? Divide both sides by -2 and you have (x-1)=4 x=5 simple.
That’s what I did too!
But distributing second line is wrong -2.-1=2, not -2
It’s more to do with the usual method of simplification like with PEMDAS/BODMAS, but there is always multiple ways to get to the same answer.
No reason you can’t distribute. It’s math. All roads lead to Rome. -2x+2=-8, -2x=-10, x=5. -2(4)=-8.
There’s more than one way.
X=5
Yes I did solve the problem and thanks to your teachings I now can solve basic algebra problems.
2 years ago I would have been totally lost and then I stumbled on your TabletClass and rediscovered my interest for mathematics.
It gives me pause in a world getting crazier by the day. ;)
Now, I need to be careful because you came up with this "finding the error" teaching strategy. I get what you're doing here.
But I trust my newly acquired foundation. :)
This one was easy if we don't think about the possible errors: (x - 1) = minus 8/minus 2, (x -1) = 4, x = 5
What I did:
Expand brackets
-2x + 2 = -8
Get all unknown terms on one side and known terms on the other
-2x = -10
Divide
x = 5
There are 2 mistakes I see in the working shown in the video:
1. Line 2 - a negative multiplied by a negative is always a positive. Here, however, they have done -2 * -1 = -2, which is incorrect.
2. Even if it had been correct up to this point, they have made a mistake when dividing for line 4. Similar to multiplying, when dividing a negative by a negative, you get a positive. They have done -6 / -2 = -3, which is also incorrect.
Therefore, I recommend to the person who wrote this (idk and idc if they are real) to learn more about multiplying with negative numbers.
3 mistakes as you wrote them 😀😀😀
@@batavuskoga what
@@Hi-rw8vr The way you wrote and solved is correct, but in the video it's not shown like that
@@batavuskoga well I’m not recording it, and I wrote this before watching the video like I do with all of them.
Thank you
Obviously, the "student" in this example needs to work on multiplying/dividing by, as well as adding and subtracting, negative numbers
In the first step, distributing the -2 in -2 ( x - 1), that side should work out to -2x + 2, since multiplying a negative by a negative resulsts in a positive value.
In the second step, we subtract the + 2 from both sides, meaning that step should end with -2x = -10, rather than -2x = -6.
And so, the final step, dividing both sides by -2 to solve for x should end with x = 5, rather than x = -3....
(Answer composed at 1:11 into the video, where I could clearly see the "student's" work.)
You can also multiply the equation by -1 and clear out the negative signs (or simply erase them)
Greetings. Erasing the signs is not an acceptable way of getting rid of the minus signs.
The error is in distributing the -2.
But more fundamentally, if you think that multiplying all those negatives is more error-prone then the error is leaving yourself with that problem at all.
Just eliminate the negative signs (ie multiply both sides of the equation by -1) to leave
2(x-1) = 8
Now when you distribute there's no pesky negative × negative.
That's if you bother with distribution at all. You could just divide both sides by 2
x-1 = 4
and the solution is obvious. (As other people have said, you get to this point in one step if you start by dividing both sides by -2).
When you've gone wrong, "what did I do wrong?" is one question to ask yourself, but don't forget to think about "is there a different way to approach this problem?" too.
got 5 no errors simple 10 seconds thanks for the fun
Can we seniors purchase/take courses if we are not enrolled in any school?
Greetings. There is no identifiable error in the expression. The expression
-2(X-1)=-8 gives
X=5. There is error in the student's work, not the expression given.
-2(x-1) =-8
-2x + 2 = -8
-2x = -8 -2
-2x = -10
2x = 10
x = 10 divided by 2
x = 10/2 = 5
x = 5
Thank you. I got the right answer. 😊
-2(x-1)=-8
(X-1)=-8/-2
X-1=4
X=4+1
X=5
Is the answer 4?
I did this: - 2(X-1)=
-2x -1 +1= 2
-2x/-2 = 2.2
X= 4
-2 (x -1 ) = -8
-2x +2 =-8
-2x = -8 -2
-2x=-10
2x = 10
X = 5.
I wonder why you did not suggest my method to solve this problem though. ;)
I solved this in my head in about 4 seconds. No steps necessary.
I also got 5 very quickly, but the other part was to find the mistakes his student made, so it doesn’t really work to say I got 5 and didn’t make mistakes. I did find the students mistakes.
5
-2(x-2)=_2x+4
This is too easy and difficult - I know the distributive properties YET I knew this was so easy and rushed and made mistakes by forgetting to also multiply the negative 2 by negative one so I ended up with the wrong answer! I think we should treat all equations, easy or hard, with great respect and avoid rushing.
Answer is 4
Mistake one: they did not show that -2 * -1 is 2 and even IF the -2 was correct due to it being (x + 1), then
Mistake two: -6 divided by -2 is NOT -3. Student did NOT prove their work. So.......
Mistake three: ALLWAYS PROVE AND SHOW YOUR WORK!!!!!!!!!!!!!!!!!!!!!!!
Proper answer:
-2x + 2 = -8
-2x = -10
x = 5
Prove your work by substituting in x = 5
-2[5] + 2 = -8
-10 + 2 = -8
-8 = -8
This proves that x does in fact equal 5 and it is the only solution.
Anything less and it is 100% wrong.
Easy
The correct answer is 5
You know that -2 x 4 = -8. So what minus one is four?
x = +5
The mistake is +2 not -2
No error.
How the equation in the thumbnail has errors.
-2 should be 2.
As in mathematics, fundamentals do matter, the same as with language. Anytime you use the word, "if" or "wish", the subjunctive, "were", and not the term, "was", is to be used. Sorry, but it hurts my ears.
I am very appreciative of the work that you do in the advancement of mathematics, though.
It isn't "libary" it's "library" - pronounce both R's man!
Every line from the second line has a mistake, so 3 mistakes
There are errors on lines 2 and 4 but not line 3.
-2x = -6 follows correctly from -2x - 2 = -8.
@@gavindeane3670 Yes, the follow-up is correct, but line 2 is wrong.
5
X =5
5
X=5
X=5
X=5
x=5
x =5
x=3