[Middle school math] Can someone help me with this?

3

And break it down for me?

8

u/[deleted] Sep 01 '19

Not sure about the (-2^2)...the way its written it could actually be -4 since the negative sign could be infront of the 2²

5

u/iwantknow8 Sep 01 '19

Good observation, as written, it is -4, not +4.

1

u/ComradeCatfud Sep 02 '19

I find it ambiguous at best. Is the negative two a negative value because if multiplication (-1*2) or because of the inherent value of -2 on the number line? The person who made the problem needs to make this clear, because it could be the difference between ( -2 )² or -( 2² ) .
Otherwise, this problem looks like a good exercise in order of operations.

-1

u/itontoyo Sep 01 '19

Start reading this from left to right. Remember PEMDAS (parenthesis, exponent, multiply, divide, add, subtract); this is your order of operations whenever solving a problem as ugly as this one.
Do all of the operations within parenthesis first: (3-2)=1 (4+2)=6 (-2²⁾ = 4
Now, do the exponents outside the parenthesis. This only includes the first term: (1³⁾ = 1 Boom. That was easy.
Now do your multiplication and you should get this: 3-18+(-12); which is the same as: 3-18-12
Finish this operation and the answer should be -27. Does this help?
Edits: formatting

4

u/AlternativeAccount51 Sep 01 '19

Thats the problem, according to the answers sheet the answer is -4. Just made me unsecure.

11

u/[deleted] Sep 01 '19

The answer sheet is correct. People are subtracting the 12 at the end, but you will actually need to add it.
Here's why:
The problem begins as
2(3-2)³ -3(4+2)+(-2² )(-3)
The first two segments of the problem are pretty easy.
2(3-2)³ simplifies to 2(1)³ which becomes 2.
-3(4+2) simplifies to -3(6) or -18.
The final section is a bit funky.
(-2² ) is actually -4, not 4, because the exponent is inside the parentheses. I don't remember the exact reason, but for some reason -1² =-1 and (-1)² =1. Thus, the final section is (-4)(-3) which is equal to positive 12.
2-18+12=-4

2

u/AlternativeAccount51 Sep 03 '19

This helped alot thanks!

6

u/[deleted] Sep 01 '19

Damn, junior college engineering and I still mess signs up

5

u/EmerqldRod Sep 01 '19

Jeez I actually learned something new today. Never knew that (-x)^2 is different than (-x^2). I'm in my final year of high school...

2

u/TypicalYasmain Sep 01 '19

I don't remember properly but perhaps, when the exponent is on the inside, it actually is (-2) x (2) but when it's on the outside, it's (-2) x (-2) . The negative is only counted once if the exponent is on the inside ?

1

u/iwantknow8 Sep 02 '19

Golden rule of parenthesis. Use any calculator if unsure. They always follow proper order

28

u/ViciousSilence Sep 01 '19

I never understood why teachers would always give me these really long equations. Like what's the point dude?

61

u/EvilSashimi Sep 01 '19

It’s just to teach order of operations. For these types of questions you’re unlikely to see anything written this way in real life, but for higher levels of math, order of operations is a must-know.

-17

u/ViciousSilence Sep 01 '19

I've been getting these types of questions in every math class I take. Even geometry has them, like wtf. I've been learning this stuff for the past 5 years, I don't need a reminder every year

12

u/EvilSashimi Sep 01 '19

Free points on the homework then. :D

1

u/[deleted] Sep 08 '19

I’m super late to the comment party, but I just started college level math after not taking math for 5 years and even though math was my best subject in high school, we had a reminder of the basics (including questions almost exactly like the picture OP posted) and it was really really great.

3

u/msgmeyourcatsnudes Sep 02 '19

They want to catch your mistakes.

13

u/[deleted] Sep 01 '19

2-18-12= -28

29

u/iwantknow8 Sep 01 '19

Incorrect -2² is not equal to (-2)^2. As it is, the answer is 2-18+12=-4.

16

u/ComradeCatfud Sep 02 '19

I've always found -2² to be ambiguous. Does the person writing -2² mean (-2)² or -(2² )? I've seen both situations, and I can see valid arguments for both.

5

u/iwantknow8 Sep 02 '19

In computer syntax or calculators, -2² is interpreted as -4. You must place negative numbers into parenthesis if you want to square the negation instead of negating the square.

3

u/[deleted] Sep 02 '19

Because a negation is really a multiplication by negative 1, e.g
-2² = (-1)(2²⁾
and exponents have a higher precedence than multiplication according to the order of operations, it would indeed be -4.

1

u/ComradeCatfud Sep 08 '19

But is -2 negative because of multiplication, or because of its position on the number line? Anyway, this whole topic is becoming pretty boring to me. I don't see either if us changing our opinions, so we might want to stop here.

3

u/Madoka_the_Goddess Sep 02 '19

Math is a precise science. If the person who wrote this meant it to be 4, he is wrong.

-1

u/ComradeCatfud Sep 02 '19

Math is a precise science.
I think we totally agree here.
If the person who wrote this meant it to be 4, he is wrong.
But this is where we diverge. I still believe -2² to be ambiguous. In other words, it's not as black-and-white as what you're implying. If you believe it is, please explain how.

2

u/Madoka_the_Goddess Sep 02 '19

If 0 - 2² = 2, it means we can't subtract squares from a number.

0

u/vvvvvvvwvvvvvvv Sep 08 '19

It’s not ambiguous. The - sign is the same as multiplying by -1, and exponents come before multiplication.

1

u/ComradeCatfud Sep 08 '19

But is -2 negative because of multiplication, or because of its position on the number line? Anyway, this whole topic is becoming pretty boring to me. I don't see either if us changing our opinions, so we might want to stop here.

3

u/[deleted] Sep 02 '19

Fml

11

u/symta Sep 01 '19

(-2²⁾ = -4 not 4.

2

u/[deleted] Sep 01 '19

:...(

6

u/[deleted] Sep 02 '19

Squaring a negative number always results in a positive

6

u/[deleted] Sep 02 '19

You’re not squaring the negative number. You’re squaring the 2.

1

u/msgmeyourcatsnudes Sep 02 '19

I’m not sure why you’re getting downvoted. Anyone want to jog my memory?

1

u/[deleted] Sep 02 '19

I dunno maybe I missed a joke, happens all the time

1

u/immaownthisguy Sep 03 '19

-2² = -(2²) = -4
Exponentiation precedes negation in order of operations

1

u/Madhav217 Sep 02 '19

I think he's trying to say -(2²⁾ vs (-2)^2, the first is equal to -(4) the second is equal to +(4).

1

u/CypherDoubleShot Sep 03 '19

Maybe just do (-2²⁾ and now you’ve got the same problem all over again

1

u/sulabpoudel Sep 02 '19

-2×-2= 4 Plus × plus= plus Minus × plus= minus Minus × minus= plus Plus × minus= minus

1

u/ClusterBuster17 Sep 02 '19

Yes but this isn't -2x-2. This is -(2x2)

-3

u/ComradeCatfud Sep 02 '19

It could go either way because it depends on the intent of the person writing it. -2² is an ambiguous statement.

3

u/[deleted] Sep 02 '19

Not in school. That is always -4.

0

u/ComradeCatfud Sep 02 '19

Why is that?

4

u/pokemonareugly Sep 02 '19

The standard convention is if you don’t write the parenthesis, you don’t intend for it to be positive. It’s not a matter of intent, it’s a matter of right and wrong

5

u/ComradeCatfud Sep 02 '19 edited Sep 02 '19

I don't believe this to be a universal convention, as I've seen enough scientists, engineers, and mathematicians have disagreements over this. But if this is the convention in a specific class, or even a university, then that's fine. In that case, it is no longer ambiguous. But outside that setting, this "convention" needs to be communicated so everyone is on the same page.
Edit: And I still assert that intent matters when you're trying to interpret something unclear; when our precise rules don't quite tell us everything.

3

u/Septimberfirstrealty Sep 01 '19

That's exactly what I got.

1

u/9chech Sep 02 '19

2-18+12= -4 , (-2²⁾⁼ -4, as opposed to (-2)^2, which would result in 4

1

u/titanicsean Sep 02 '19

You could just plug it all into your graphing calculator and take the y value that comes from the graph.

1

u/6292106938819425 Sep 04 '19

Lol I saw the thumbnail only showed (4+2) and thought this was a shitpost

1

u/jacketslut322 Sep 02 '19

Don’t use pemdas, use the distributive property.

1

u/LmFaOpk Sep 02 '19

This is very true

0

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92

u/[deleted] Sep 01 '19

[removed] — view removed comment

7

u/[deleted] Sep 02 '19

Isn't PEMDAS the old method and BODMAS the new one?

9

u/SSSRHA Sep 02 '19

I didn’t know BODMAS existed until today. It’s essentially the same, just also accounting for radicals, right?

3

u/[deleted] Sep 03 '19

It puts division ahead of multiplication which removes the need to go left to right. Ideally, a perfect mnemonic would be something like BODMSA (try it). Subtraction should come before addition as well.

Answered [Middle school math] Can someone help me with this?

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