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C3 help needed

Need help with Q4.

I done part A by rearranging, need help with part B
image.jpg184.9KB
Original post by Vorsah
Need help with Q4.

I done part A by rearranging, need help with part B

What don't you get?
Reply 2
Avatar for arkanm
arkanm
5
Just so you know why it works (I've never done numerical methods before, but I played around with it a bit and it's making sense):

Basically you want to approximate 12\sqrt{12}. To do this, it's reasonable to start out with an equation that has 12\sqrt{12} as the solution, namely

x2=12x^2=12.

Now divide both sides by 2x to get

x2=6x\frac{x}{2}=\frac{6}{x}.

Add x/2 to both sides to get

x=x2+6x=12(x+12x)x=\frac{x}{2}+\frac{6}{x}=\frac{1}{2}\left(x+\frac{12}{x}\right)

  ⟺  x=12(x+12x)\iff x=\frac{1}{2}\left(x+\frac{12}{x}\right).


Look familiar to you? :wink:
Reply 3
Avatar for Vorsah
Vorsah
OP
5
Original post by keromedic
What don't you get?



All of part B, I don't know where to start
Original post by Vorsah
All of part B, I don't know where to start


Just do what it says. Put in a value for x, say 11 or 12, since sqrt(127) is between 11 and 12 and work out the next value of x. Then use this value and repeat until you get no change in the 5th decimal place.

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