Solving for a 'base' (eg binary) in a quadratic equation

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Discussion Overview

The discussion revolves around determining the base of a quadratic equation given its roots. Participants explore the relationship between the coefficients of the equation and their representation in an unknown base, focusing on the quadratic equation x² - 11x + 22 = 0, with roots at x = 3 and x = 6.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Exploratory

Main Points Raised

  • One participant presents an equation and attempts to express the base as a variable r, leading to a derived formula r = (7-10x)/(1-x).
  • Another participant notes that since 3 and 6 are roots, the base must be at least 6 and discusses the factorization of the quadratic.
  • Comparisons are made between coefficients of the quadratic in an unknown base and their decimal equivalents, leading to a set of equations that must hold true for the base.
  • A later reply suggests that the base could be 8, referencing the conversion of numbers from base 8 to decimal.
  • Another participant confirms the base by demonstrating the conversion of numbers from base 8 to decimal, showing the calculations for 118 and 228.

Areas of Agreement / Disagreement

There is a suggestion that the base is 8, and some participants seem to agree with this conclusion, but the discussion does not explicitly confirm a consensus on the base being definitively established.

Contextual Notes

Participants express uncertainty regarding the integer nature of the base and the implications of the derived equations. The discussion does not resolve whether other bases could also satisfy the conditions presented.

Who May Find This Useful

Students or individuals interested in quadratic equations, base conversions, and mathematical reasoning related to algebraic expressions may find this discussion useful.

General_Sax
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Homework Statement


The solution of the quadratic equation x2 - 11x + 22 = 0 are x = 3 or x = 6. What is the base of the numbers?


Homework Equations


Knowledge of how to convert from a generic base to decimal?


The Attempt at a Solution



I tried to just place r in where I would have a value of s*r1

(x-3)(x-6) = x2 - 11x + 22

x2 - 6x - 3x + [1*r + 8] = x2 - [x( r + 1)] + 2r + 1

r + 8 - 9x = x + 2r - xr + 1

7 - 10x = r(1-x)

r = (7-10x)/(1-x)

when I try to put either of the values of x in I get r as either 10.6 or 11.5

Please help me.
 
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General_Sax said:

Homework Statement


The solution of the quadratic equation x2 - 11x + 22 = 0 are x = 3 or x = 6. What is the base of the numbers?


Homework Equations


Knowledge of how to convert from a generic base to decimal?


The Attempt at a Solution



I tried to just place r in where I would have a value of s*r1

(x-3)(x-6) = x2 - 11x + 22

x2 - 6x - 3x + [1*r + 8] = x2 - [x( r + 1)] + 2r + 1

r + 8 - 9x = x + 2r - xr + 1

7 - 10x = r(1-x)

r = (7-10x)/(1-x)

when I try to put either of the values of x in I get r as either 10.6 or 11.5
The base should be an integer.

Since 3 and 6 are roots of the equation, it's safe to assume that the base is at least 6.
Also, since 3 and 6 are roots, x - 3 and x - 6 are factors of the quadratic.

On the one hand you have (x - 3)(x - 6) = x2 - 9x + 18 (in base-10).
On the other hand, you have x2 - 11x + 22 (in unknown base).

Comparing the coefficients of the first expression with the second, you must have
110 = 1b
-910 = -11b
1810 = 22b

What does b need to be so that all three equations are true statements?
Note that d1d2 in base b = d1 * b + d2 in base 10.
 
It's base 8 right?
 
Right. Notice that 118 means 1*8 + 1*1 = 910, and 228 means 2*8 + 2*1 = 1810.
 

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