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# AS Maths: "Factorise the following equations and then sketch the curves" watch

1. I'm back!

Right, I think I've done the first one right but I'm stuck with the other four.

b) y = x^3 + 5x^2 + 4x

= (x+0)(x+4)(x+1)?

d) y = 3x + 2x^2 - x^3

f) y = x - x^3

h) y = x^3 - x^2 - 2x

j) y = x^3 - 9x^2
2. first one is correct

what are you stuck on with the other 4?
3. Yeah. What matt2k8 has said really and post some working along with it
4. Well for d:

y = 3x + 2x^2 - x^3

y = -x^3 + 2x^2 + 3x

Then I can't factorise it from here? Or do I have to use the formula?
5. take out a power of x, so you have
x(-x^2 + 2x + 3)
6. (Original post by Meleky)
I'm back!

Right, I think I've done the first one right but I'm stuck with the other four.

b) y = x^3 + 5x^2 + 4x

= (x+0)(x+4)(x+1)?

d) y = 3x + 2x^2 - x^3

f) y = x - x^3

h) y = x^3 - x^2 - 2x

j) y = x^3 - 9x^2
for (d)(f)(h), just like you did with question (b), take out 'x' first
7. (Original post by mespannerhanz)
take out a power of x, so you have
x(-x^2 + 2x + 3)
Then what? Brain is effing dead.
8. (Original post by Meleky)
Then what? Brain is effing dead.
Then factorise . If it helps, write it as and then factorise (I find it easier this way).

Each of these questions is the same: pull out common factors and then factorise what's left. If you can do one you should be able to do the rest.
9. (Original post by nuodai)
Then factorise . If it helps, write it as and then factorise (I find it easier this way).

Each of these questions is the same: pull out common factors and then factorise what's left. If you can do one you should be able to do the rest.
So (x+3)(x-1)(x+0)?

And how comes you can just add a minus to everything? FFUU.
10. (Original post by Meleky)
So (x+3)(x-1)(x+0)?

And how comes you can just add a minus to everything? FFUU.
be careful with + and -
11. (Original post by IAmTheChosenOne)
be careful with + and -
(x+3)(x-1)(0-x)?
12. (Original post by Meleky)
So (x+3)(x-1)(x+0)?

And how comes you can just add a minus to everything? FFUU.
If you take a factor of -1 out then the signs get flipped. That is, .

Now, factorising should give and not . As such, .

Also, when you're factorising things, you don't need to write , you can write .

The answer in this case would therefore be . To tidy it up a bit we can use the fact that to write this as .

Now you can do the rest. Remember:
1. Take out common factors
2. Factorise what's left (and if it's easier, take a factor of -1 out as well).
13. (Original post by nuodai)
If you take a factor of -1 out then the signs get flipped. That is, .

Now, factorising should give and not . As such, .

Also, when you're factorising things, you don't need to write , you can write .

The answer in this case would therefore be . To tidy it up a bit we can use the fact that to write this as .

Now you can do the rest. Remember:
1. Take out common factors
2. Factorise what's left (and if it's easier, take a factor of -1 out as well).
You beautiful brute. Thanks so much.

I'm now stuck with f though (y = x - x^3).

I'm guessing you change it to y = -x^3 + x but then what?
14. (Original post by Meleky)
You beautiful brute. Thanks so much.

I'm now stuck with f though (y = x - x^3).

I'm guessing you change it to y = -x^3 + x but then what?
Common factors...
15. (Original post by Meleky)
You beautiful brute. Thanks so much.

I'm now stuck with f though (y = x - x^3).

I'm guessing you change it to y = -x^3 + x but then what?
Common factor of x, like all the others.
16. (Original post by nuodai)
Common factors...
y = -x^3 + x

y = -x(x^2 - 1) or y = x(-x^2 + 1)?

And then what?
17. Both expressions are the same
18. (Original post by Meleky)
y = -x^3 + x

y = -x(x^2 - 1)?

Then what?
Forgive my rudeness, but I can't tell if you're trolling or just have a really short memory. For the benefit of the doubt, I'll repeat what I said in my other post:
1. Take out common factors
2. Factorise what's left (and if it's easier, take a factor of -1 out as well).
So what do you think is next?
19. (Original post by nuodai)
Forgive my rudeness, but I can't tell if you're trolling or just have a really short memory. For the benefit of the doubt, I'll repeat what I said in my other post:

So what do you think is next?
I remember what you said, I just don't know how to "factorise what's left".
20. (Original post by Meleky)
I remember what you said, I just don't know how to "factorise what's left".
I'm fairly confident that you can factorise if you put your mind to it.

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