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# v.quick functions question watch

1. hey

I came across this while doing some past papers, I am wondering that this function means

for example so what would ?
I thought it means square the f(x) but that answer in the mark scheme isn't

thanks a lot
2. I think it means do the function twice, so . In this case, . I'm not certain, though. Have you got the right answer in the mark scheme?

It could just about mean second derivative of f, but that would be horribly non-standard notation.
3. (Original post by Tempeststurm)
I think it means do the function twice, so . In this case, . I'm not certain, though. Have you got the right answer in the mark scheme?

It could just about mean second derivative of f, but that would be horribly non-standard notation.

just another question:

a curve has the equation: and a line crosses the curve

There are two points of intersection 0 and -2
I can't algebrically solve it to get -2 I keep getting 0.
4. well you just solve
(x+2)e^-x=(x+2)
that means that (x+2)[e^-x)-1]=0 substracting
Therefore x+2=0 OR (e^-x)-1=0
so x=-2 or e^-x=1, that is x=0
that's it your error I think was to divide both sides by x+2...you cannot do this if x+2=0 so basically you loose a solution
5. (x+2)(e^-x -1)=0

so e^-x -1 =0 or x+2 = 0

so x = 0 or -2
6. (Original post by paronomase)
well you just solve
(x+2)e^-x=(x+2)
that means that (x+2)[e^-x)-1]=0 substracting
Therefore x+2=0 OR (e^-x)-1=0
so x=-2 or e^-x=1, that is x=0
that's it your error I think was to divide both sides by x+2...you cannot do this if x+2=0 so basically you loose a solution
sorry i don't get this part, how did you get this from both the equations...mind explaining this in detail?
7. (Original post by New Username)
sorry i don't get this part, how did you get this from both the equations...mind explaining this in detail?

taking out a factor of (x+1)
8. (Original post by Tallon)
taking out a factor of (x+1)
I was actually talking about the subtracting but I just got it now!
Yeah I was dividing both sides by (x+2) which meant I was loosing one of the solutions. Thanks a lot for your help

Thanks everyone!

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