Math HSC 2003 Q7 help please (1 Viewer)

[Twickel]

Hi
How do I find he common ration for Q7 a (i)

Its 2/root2-1/2

sohw working please.

I keep getting Root2+1/1 but it should be the inverse of that 1/root+1

WHY?

 

[vds700]

The common ratio is 1/(sqrt2 + 1)

Now to find the limiting sum, use the formula

S = a/(1-r)
=2/[1-(1/(sqrt2 +1))]
=2/[(sqrt2 + 1 - 1)/(sqrt2 + 1)]
=2/[sqrt2/(sqrt2 + 1)]
=2(sqrt2 + 1)/sqrt2
=sqrt2(sqrt2 + 1)
=2 + sqrt2

 

[Shoom]

I need help finding the common ratio,

also can you help with http://www.boardofstudies.nsw.edu.au/hsc_exams/hsc2004exams/pdf_doc/maths_04.pdf

question 7c

thankyou.

 

[vds700]

I found the common ratio by inspection, however u can find it by dividing one term by the previous ter,

e.g [2/(sqrt2 + 1)^2]/[2/(sqrt2 + 1)
=1/(sqrt2 + 1) once u simplify down a bit