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# how do you work out 4(a+1)(a-8) watch

1. (Original post by ombtom)

*deletes comment*

Hahaha, it's fine! I've done the same countless times.
2. (Original post by sandvika)
Multiplying 4 first would help him understand it better

Unless OP says otherwise, working out doesn't mean simplifying
Until the OP says otherwise, working out doesn't mean solving.

Oh yes, I seem to miss the fact that you know the OP inside out and the nuances of what would help him understand better or not...
3. (Original post by ombtom)
Yeah I got fed up with school maths teachers so I taught myself.
Same. My teacher wasn't very good but I was the best in the class so was allowed to just sit at the back and do maths each lesson from year 9 onwards. I wasn't very good at teaching myself at that age so only learned about quadratics 2 days before the exam, because I thought the exam was months in the future and the aforementioned teacher told me on the Friday that I had it on the Monday(I didn't know then that exam dates are released publicly).

(Original post by sandvika)
Multiplying 4 first would help him understand it better

Unless OP says otherwise, working out doesn't mean simplifying
Unless the OP says otherwise, working out doesn't mean anything specifically.
4. (Original post by Zacken)
Until the OP says otherwise, working out doesn't mean solving.

Oh yes, I seem to miss the fact that you know the OP inside out and the nuances of what would help him understand better or not...
By definition, to work out is to solve, and to solve is to find x (a in this case)
5. (Original post by sandvika)
By definition, to work out is to solve, and to solve is to find x (a in this case)
There is no such definition of "work out" in the mathematical universe defined rigorously.
6. (Original post by georgia7600)
i'm assuming you mean expand and simplify, if so you need to use foil.

this is a good technique for expanding as it gives you the answer in some quick steps. I will explain the method below.

foil-

4(a+1)(a-8) means you need to times the first brackets by 4.

Keep the numbers in the brackets ready to expand and simplify.

This will give you: (4a+4)(a-8)

you need to now times everything together (but in a certain way).

first
outer
inner
last

go in order so you multiply the first numbers together:
4a x a = 4a2

now the outer numbers:
4a x -8 = -32a

so far we have 4a2 - 32a

next multiply the inner numbers, so:
4 x a = 4a

finally the last numbers:
4 x -8 = -32

if we put it all together we get: 4a2 - 32a + 4a - 32

we now need to simplify this so we just put together the numbers that match.

4a2 is the only squared number so we leave this as it is.

However, we have two lots of numbers that have 'a' after so we do -32a + 4a = -28a

32 is also the only alone number so we leave this as well.

Put this together and it equals: 4a2 - 28a -32

simple when you know how don't hesitate to ask about anything else:u
thank you so much i love you!!!!!!!!!!!!!!
7. (Original post by lydiafoof)
First calculate the bracket (a+4)(a-8), so factor it out, after that multiply that result by the factor four. But if you want to calculate the zeros, the term in brackets is better to handle by far.

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Updated: October 21, 2015
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