Monday

September 22, 2014

September 22, 2014

Posted by **Mikal** on Saturday, March 22, 2008 at 4:26am.

r^64-1 = 2.5x10^7 (r-1)

any ideas?

- Maths -
**Reiny**, Saturday, March 22, 2008 at 9:21amr-1 is a factor of r^64 - 1 so use synthetic division (notice the pattern) to divide both sides by r-1 to get

r^63 + r^62 + ... + r + 1 = 2.5(10)^7

the left side is a geometric series with

a = 1

common ratio = r

n = 64

so the sum of the left side = 1(r^64 - 1)/63

then (r^63 - 1)/63 = 2.5(10^7

r^63 = 63(2.5)(10)^7 + 1

taking the 63rd root I got

r = 1.3922

- Maths -
**Reiny**, Saturday, March 22, 2008 at 9:46amOOOPS, just looked at my solution again and

I'm WRONG!!! (must have had an early morning synapse collapse)

The sum of my series should have said

1(r^64 - 1)/(r-1)

then r^64 - 1 = 2.5(10)^7(r-1)

which brings me back to what we started with.

Arggh!!!

Sorry, looks like we would have to use some method such as Newtons's Method or some kind of "equation solver" program.

- Maths -

**Answer this Question**

**Related Questions**

AP Chem - MnS(s) + 2 H+ --> Mn2+ + H2S(g) At 25 C the solubility product ...

Chemistry - BrO-3 + 5Br- + 6H+ ---> 3Br2 + 3H2O the value of - delta[BrO3]/...

math - standard form - please could you check the first 2 then explain the ...

maths - 5x10^2 divide by 7x10^4 what is the answer in standard form

chemistry - what is the result of adding (2.5x10^3)+(3.5x10^2) ?

Math - Name the property that justifies each step. [(2x100)+(3x10)]+[(1x100)+(...

Math - How do you solve this equation? 1.5x10^-9=(x^2)/(.858-x)

Chemistry - If the Kb of a weak base is 1.5 × 10^-6, what is the pH of a 0.25 M ...

physics - gravational force deimos, a satellite of amrs, has an average radius ...

Chemistry - 4. 5.6 x 10-6 mol of A and 5 x 10-5 mol of B are mixed in a 200 mL ...