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# factorising? watch

1. hi,

im trying to find the x and y values for the following equation: y = x(x^2 - 4)

when x = 0 y= -4
but not sure what to do when y = 0
thanks
2. i think that you have to either make the part in the braket =0. Or the actual x value being timesd by the bracket.

e.g. 0(0^2 -4)

or 2(2^2 - 4)

3. (Original post by Hrov)
i think that you have to either make the part in the braket =0. Or the actual x value being timesd by the bracket.

e.g. 0(0^2 -4)

or 2(2^2 - 4)

how did you come to do this? 2(2^2 - 4) why did you choose to sub x=2 ?
4. when y=0 you want the equation to be equal to 0
so if the part in the bracket is equal to 0, ie 2^2 -4 what ever this is timesd by outside of the bracket (2) the equation will still equal 0.

i.e. look in your brackets and make = to 0.
make your x value equal to what is being take off of it. so in this case what squared minus 4 = 0. answer being 2
5. or -2
6. (Original post by Hrov)
when y=0 you want the equation to be equal to 0
so if the part in the bracket is equal to 0, ie 2^2 -4 what ever this is timesd by outside of the bracket (2) the equation will still equal 0.

i.e. look in your brackets and make = to 0.
make your x value equal to what is being take off of it. so in this case what squared minus 4 = 0. answer being 2
i get it now
thnks
7. like mf2004 says, dont forget the -2

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