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# Stationary points...Help! watch

1. Basically, I need to find the stationary points of the equation

This is how far I've gotten,

Differentiating with respect to

Then, bringing the together, I get,

At stationary points, , so,

I don't see where I can go from here and how I can find the stationary points. I need help please?

Thanks.
2. (Original post by RamocitoMorales)

You have two equations there, what can you do with them?
3. Where (on that curve) is y equal to -2x?
4. (Original post by LetoKynes)
You have two equations there, what can you do with them?
Simultaneously solve it?
5. (Original post by LetoKynes)
You have two equations there, what can you do with them?
It still doesn't work, this is what happens.

Substituting in the y value into the first equation, I get,

That's not the right answer, the right answer should be (1,-2), (-1, 2).
6. Since when has x(-2x) equalled -4x^2?
7. (Original post by RamocitoMorales)
It still doesn't work, this is what happens.

Substituting in the y value into the first equation, I get,

Mistake on this line

That's not the right answer, the right answer should be (1,-2), (-1, 2).
Do you get the right answer if you correct that?
8. (Original post by LetoKynes)
Do you get the right answer if you correct that?
I can be such a plum sometimes, sorry about that.

So, continuing form the mistake, I get,

or

Thank you, that is the correct answer for . Now I will sub it back into the original equation to find the value for .

in this situation, so,

So now what do I do?

Thanks.
10. Yeap, just solve the quadratic equation.
11. (Original post by generalebriety)
So basically,

Which can be simplified to,

Which can be factorised as,

So or

But it's still wrong, since on the answers it says that y should equal to -2 and 2, not -2 and 1.

hmmmm

I would give you reputation, but it's worthless.
12. You can use the x = -1 and you should get the other y value

Although I'm not sure how you're supposed to know which value to use..
13. (Original post by LetoKynes)
You can use the x = -1 and you should get the other y value

Although I'm not sure how you're supposed to know which value to use..
Ah of course, I'd forgotten all about the

Now when in the equation ,

So, , or

This is a very confusing question.
14. (Original post by RamocitoMorales)
Ah of course, I'd forgotten all about the

Now when in the equation ,

So, , or

This is a very confusing question.
It's not that confusing. If x = 1 then y = 1 or -2; if x = -1 then y = -1 or 2. Which values are valid (remembering that y = -2x)? They will then all satisfy the original equation, so you're done.

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