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# The coefficient of x^3 in the expansion of (2+x)(3-ax)^4 is 30. Find the values of th Watch

1. The coefficient of x^3 in the expansion of (2+x)(3-ax)^4 is 30. Find the values of the constant a. I understand but do not know how to do it. Working would be appreciated!!
2. (Original post by SophieL1996)
The coefficient of x^3 in the expansion of (2+x)(3-ax)^4 is 30. Find the values of the constant a. I understand but do not know how to do it. Working would be appreciated!!
Yes, working would be appreciated.

What have you done?
3. I expanded using the x^3. amd then timesd it by (2+x)
4. errr wut?

First ignoring the first set of brackets, expand the (3-ax)^4 up to the x^4.

Simplify.

Multiply each term with (2+x).

Simplify.

Find coefficient of x^2.

===================

No one will show you working without you showing us that you have made a valid attempt at the question and are genuinely stuck with the question and is interested in finding out how to do the question instead of wanting to finish your homework as soon as possible.
5. (Original post by SophieL1996)
I expanded using the x^3. amd then timesd it by (2+x)
Show us?
6. (Original post by Dalilsp)
errr wut?

First ignoring the first set of brackets, expand the (3-ax)^4 up to the x^4.

Simplify.

Multiply each term with (2+x).

Simplify.

Find coefficient of x^2.

===================

No one will show you working without you showing us that you have made a valid attempt at the question and are genuinely stuck with the question and is interested in finding out how to do the question instead of wanting to finish your homework as soon as possible.
Thanks I will have a try, and it is not homework, I am revising questions that I am not very good at and need help with.
7. (Original post by BabyMaths)
Show us?
No need. Someone private messaged me showing all the working.
8. (Original post by SophieL1996)
No need. Someone private messaged me showing all the working.
And you think they helped you.
9. In maths, we don't learn via memorising answers but knowing how the steps interlink with each other and applying it in various different situations.

10. (Original post by SecretDuck)
In maths, we don't learn via memorising answers but knowing how the steps interlink with each other and applying it in various different situations.

sorry who was that a reply to ?
11. (Original post by SophieL1996)
sorry who was that a reply to ?
You, OP.
12. (Original post by SecretDuck)
You, OP.
Fo. All I needed was a little help and everyone is getting *****y about it. Pathetic.
13. (Original post by SophieL1996)
Fo. All I needed was a little help and everyone is getting *****y about it. Pathetic.
I always attempt the question and then ask for help if I'm really stuck and show all my working. Then I'm corrected on any mistakes.

This is how the maths forum works
14. Don't blame us -> you never showed any working, hence showing no proof that you actually wanted help rather than a quick answer. Its usually the etiquette that decent people show on this forum when asking for help.
15. Who really gives a damn about negative ratings?

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