When $555_{10}$ is expressed in this base, it has 4 digits, in the form ABAB, where A and B are two different digits. What base is it?
When $555_{10}$ is expressed in this base, it has 4 digits, in the form ABAB, where A and B are two different digits. What base is it?
Let the base be X
$$\\A*X^3+B*X^2+A*X+B=555\\\\
AX^3+BX^2+AX+B=555\\\\
X^2(AX+B)+(AX+B)=555\\\\
(X^2+1)(AX+B)=555\\\\
So\;\;X^2+1\;\;$must be a factor of 555$\\\\$$
$${factor}{\left({\mathtt{555}}\right)} = {\mathtt{3}}{\mathtt{\,\times\,}}{\mathtt{5}}{\mathtt{\,\times\,}}{\mathtt{37}}$$
factors of 555 are 3,5,37,15,111,185,555
5 and 37 would both work so far
5 would be base 2 And base 2 is to little, 37 would give base 6 (X=6) so that is probably correct.
Lets see
$$\\(X^2+1)(AX+B)=555\\\\
(6^2+1)(6A+B)=555\\\\
37(6A+B)=555\\\\
6A+B=15\\\\
If A=1 B=8 \qquad $no good A and B cannot be more than 5$\\\\
If A=2 B=3 \qquad $Great$\\\\
$so our number is $ 2323_6$$
Check
$${\mathtt{2}}{\mathtt{\,\times\,}}{{\mathtt{6}}}^{{\mathtt{3}}}{\mathtt{\,\small\textbf+\,}}{\mathtt{3}}{\mathtt{\,\times\,}}{{\mathtt{6}}}^{{\mathtt{2}}}{\mathtt{\,\small\textbf+\,}}{\mathtt{2}}{\mathtt{\,\times\,}}{\mathtt{6}}{\mathtt{\,\small\textbf+\,}}{\mathtt{3}} = {\mathtt{555}}$$
And that is excellent
So $$555_{10}=2323_6$$
When $555_{10}$ is expressed in this base, it has 4 digits, in the form ABAB, where A and B are two different digits. What base is it?
Let the base be X
$$\\A*X^3+B*X^2+A*X+B=555\\\\
AX^3+BX^2+AX+B=555\\\\
X^2(AX+B)+(AX+B)=555\\\\
(X^2+1)(AX+B)=555\\\\
So\;\;X^2+1\;\;$must be a factor of 555$\\\\$$
$${factor}{\left({\mathtt{555}}\right)} = {\mathtt{3}}{\mathtt{\,\times\,}}{\mathtt{5}}{\mathtt{\,\times\,}}{\mathtt{37}}$$
factors of 555 are 3,5,37,15,111,185,555
5 and 37 would both work so far
5 would be base 2 And base 2 is to little, 37 would give base 6 (X=6) so that is probably correct.
Lets see
$$\\(X^2+1)(AX+B)=555\\\\
(6^2+1)(6A+B)=555\\\\
37(6A+B)=555\\\\
6A+B=15\\\\
If A=1 B=8 \qquad $no good A and B cannot be more than 5$\\\\
If A=2 B=3 \qquad $Great$\\\\
$so our number is $ 2323_6$$
Check
$${\mathtt{2}}{\mathtt{\,\times\,}}{{\mathtt{6}}}^{{\mathtt{3}}}{\mathtt{\,\small\textbf+\,}}{\mathtt{3}}{\mathtt{\,\times\,}}{{\mathtt{6}}}^{{\mathtt{2}}}{\mathtt{\,\small\textbf+\,}}{\mathtt{2}}{\mathtt{\,\times\,}}{\mathtt{6}}{\mathtt{\,\small\textbf+\,}}{\mathtt{3}} = {\mathtt{555}}$$
And that is excellent
So $$555_{10}=2323_6$$