math Calculate "(2a+8b)(4a-2b)"

[-Alex-]

Hi all,

I'm interested in becoming a pilot and was just reading some information online at a pilot programme. They give a sample entrance exam, and on it is this question (question 9):

Calculate:

(2a+8b)(4a-2b)

Is this supposed to read (2a+8b)+(4a-2b)=0, or am I missing something?

I'm not looking for the answer to this question, rather, how to calculate it; for my own knowledge.

Thanks!

[XerXis]

(2a+8b)(4a-2b)=8a^2 - 4ab + 32ab - 16b^2=8a^2 + 28ab - 16b^2

probably just to see if you know your distribution rule :)

[abecedarian paradoxious]

It would be read as "(2a+9b)*(4a-2b)" with no absolute answer: you would be solving for one variable in terms of the other: as in "a=something b" or "b=something a"

[Neo003]

Hi all,

I'm interested in becoming a pilot and was just reading some information online at a pilot programme. They give a sample entrance exam, and on it is this question (question 9):

Is this supposed to read (2a+8b)+(4a-2b)=0, or am I missing something?

I'm not looking for the answer to this question, rather, how to calculate it; for my own knowledge.

Thanks!

6a-6b

a-b

[Xahid]

Is this supposed to read (2a+8b)+(4a-2b)=0, or am I missing something?

No, I believe it means (2a+8b)x(4a-2b)=0

Since brackets () mean multiplication so its not necessary to use 'x' specifically.

[-Alex-]

I was going through the exam slowly, working out each answer in my head... I just decided to scroll through it fully, and saw that the answers are at the end. It says:

8a²+28ab-16b²

So XerXis was correct.

[strotee]

FOIL (First Outside Inside Last)

this takes me back

[GreenMartian]

.. its not necessary to use 'x' specifically.

Exactly. The same way that everyone knows 2b means 2xb.

a(2b) = a times 2 times b.

[abecedarian paradoxious]

I was going through the exam slowly, working out each answer in my head... I just decided to scroll through it fully, and saw that the answers are at the end. It says:

So XerXis was correct.

Every time I had ?'s like that in school we had to solve for each variable.... Oh well, good thing I'm not a pilot.

[XerXis]

Every time I had ?'s like that in school we had to solve for each variable.... Oh well, good thing I'm not a pilot.

That would be true if there was an equation, however it wasn't there. Also it's impossible to solve an equation with two variables. It wouldn't make any sense :)

[Axel]

I'm a pilot and as far as I can help with that question would be to interpret it as (2a+8b)*(4a-2b). Any further than that is fairly lost on me! I don't remember my entrance exams being like that!

[mercenary]

http://www.wolframalpha.com/input/?i=%282a%2B8b%29%284a-2b%29

That should help you understand

[+Nik Louch Subscriber²]

Why is this ridiculously simple thing being posted again?

It's been solved and debated to death less than 3 months ago.

[-Alex-]

Why is this ridiculously simple thing being posted again?

It's been solved and debated to death less than 3 months ago.

1) I didn't see the thread 3 months ago

2) Good luck searching the forums for a random equation

3) What's the big deal?

[+Xinok Subscriber²]

[-Alex-]

Good video (Y)