C4 binomial theorem
part a) find binomial expansion of (1+2x)^(-1/2)
my answer: 1-x+3x/4
part b) using part a show with x=-0.1 sqr(5)=2.23
by substituting in -0.1 and multiplying by 2 i only get 2.215
What have i done wrong?
my answer: 1-x+3x/4
part b) using part a show with x=-0.1 sqr(5)=2.23
by substituting in -0.1 and multiplying by 2 i only get 2.215
What have i done wrong?
(edited 7 years ago)
Original post by TheGreatPumpkin
part a) find binomial expansion of (1+2x)^(1/2)
my answer: 1-x+3x/4
part b) using part a show with x=-0.1 sqr(5)=2.23
by substituting in -0.1 and multiplying by 2 i only get 2.215
What have i done wrong?
my answer: 1-x+3x/4
part b) using part a show with x=-0.1 sqr(5)=2.23
by substituting in -0.1 and multiplying by 2 i only get 2.215
What have i done wrong?
Your expansion.
It should be 1 + x - x^2 / 2.
Check it again.
Original post by Zacken
Your expansion.
It should be 1 + x - x^2 / 2.
Check it again.
It should be 1 + x - x^2 / 2.
Check it again.
Sorry I made a mistake typing it was (1+2x)^-(1/2) I've changed it now
Original post by TheGreatPumpkin
Sorry I made a mistake typing it was (1+2x)^-(1/2) I've changed it now
Your expansion is still wrong. It should be
Original post by Zacken
Your expansion is still wrong. It should be
I don't understand, to work out the co-efficient of x^2 don't you (-0.5)(-1.5)(2)/2 which gives 3/4,
like the formula n(n-1)/2
Original post by TheGreatPumpkin
I don't understand, to work out the co-efficient of x^2 don't you (-0.5)(-1.5)(2)/2 which gives 3/4,
like the formula n(n-1)/2
like the formula n(n-1)/2
Original post by DFranklin
You might want to find the expansion of and then replace y by 2x...
That's just 1 - x/2 + 3x^2 /8
1/2^2= 1/4
1/4 +1/2 is 3/4
(3/4)/2=3/8
can I see your working out please?
(edited 7 years ago)
the coefficient of x is also squared in the x^2 term
Original post by TheGreatPumpkin
I don't understand, to work out the co-efficient of x^2 don't you (-0.5)(-1.5)(2)/2 which gives 3/4,
like the formula n(n-1)/2
like the formula n(n-1)/2
As the above posts suggest, it'll be (-0.5)(-1.5)(2)/2 * (2x)^2
Original post by Andrew Dainty
the coefficient of x is also squared in the x^2 term
Oh thank you
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