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Zorluk: OrtaNumber Bases and Conversions

If 203n114n=45n203_n - 114_n = 45_n, where nn represents a positive integer base, what is the value of nn?

  1. 66Cevap
  2. B
    55
  3. C
    77
  4. D
    88

Cevap

The correct base is 66.
Expanding the numbers in terms of powers of nn gives (2n2+3)(n2+n+4)=4n+5(2n^2 + 3) - (n^2 + n + 4) = 4n + 5. Grouping like terms results in the quadratic equation n25n6=0n^2 - 5n - 6 = 0. Factoring yields (n6)(n+1)=0(n - 6)(n + 1) = 0, giving n=6n = 6 as the only valid positive integer solution greater than 55.

Adım Adım Çözüm

1
Convert each term from base nn to base 10 using positional expansion.
203n=2n2+0n+3=2n2+3203_n = 2n^2 + 0n + 3 = 2n^2 + 3, 114n=1n2+1n+4=n2+n+4114_n = 1n^2 + 1n + 4 = n^2 + n + 4, and 45n=4n+545_n = 4n + 5.
Converting all terms to a common decimal representation allows algebraic manipulation.
2
Substitute the expanded terms back into the original equation and simplify.
(2n2+3)(n2+n+4)=4n+5    n2n1=4n+5(2n^2 + 3) - (n^2 + n + 4) = 4n + 5 \implies n^2 - n - 1 = 4n + 5.
Carefully distribute the negative sign across all terms of (n2+n+4)(n^2 + n + 4).
3
Rearrange the expression into standard quadratic form ax2+bx+c=0ax^2 + bx + c = 0.
n25n6=0n^2 - 5n - 6 = 0.
Subtracting 4n+54n + 5 from both sides sets the quadratic equation to zero.
4
Factor the quadratic equation to find the valid base nn.
(n6)(n+1)=0    n=6(n - 6)(n + 1) = 0 \implies n = 6 or n=1n = -1.
Since a base must be a positive integer strictly greater than any digit present in the equation (maximum digit is 55), n=6n = 6.

Anahtar Kavram

Solving unknown base equations using polynomial expansion in positional notation.
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