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If 554b is the base b representation of the square of the number whose base b representation is 24b then find b.

 

I've had tons of trouble with this problem. I am practicing different bases and would appreciate help!

 May 28, 2016

Best Answer 

 #2
avatar+23251 
+11

24b  =  2·b + 4

(24b)2  =  (2·b + 4)·(2·b + 4)  =  4b2 + 16b + 16

 

554b  =  5·b2 + 5·b + 4  =  5b2 + 5b + 4

 

Since these are equal:  5b2 + 5b + 4  =  4b2 + 16b + 16

     --->                          b2 - 11b - 12  =  0

     --->                        (b - 12)(b + 1)  =  0

     --->              Either  b = 12  or  b = -1

     --->     Since the base is positive,  b = 12

 

If you want to check this:  2412  =  2·12 + 4  =  26  (base ten)

     --->                                (2412)2  =  (26)2  =  784  (base ten)

Also:     55412  =  5·(12)2 + 5·(12) + 4  =  784  (base ten)      <---   They are equal!

 May 28, 2016
 #1
avatar
0

It is not clear to me what you are trying to do. If you are trying to convert a number from one base to another, then there is a procedure to do it: Example: convert 100 from base 10 to base, 2, base 4 and base 5. Then you get these answers:1100100_2, 1210_4, 400_5........etc.

 May 28, 2016
 #2
avatar+23251 
+11
Best Answer

24b  =  2·b + 4

(24b)2  =  (2·b + 4)·(2·b + 4)  =  4b2 + 16b + 16

 

554b  =  5·b2 + 5·b + 4  =  5b2 + 5b + 4

 

Since these are equal:  5b2 + 5b + 4  =  4b2 + 16b + 16

     --->                          b2 - 11b - 12  =  0

     --->                        (b - 12)(b + 1)  =  0

     --->              Either  b = 12  or  b = -1

     --->     Since the base is positive,  b = 12

 

If you want to check this:  2412  =  2·12 + 4  =  26  (base ten)

     --->                                (2412)2  =  (26)2  =  784  (base ten)

Also:     55412  =  5·(12)2 + 5·(12) + 4  =  784  (base ten)      <---   They are equal!

geno3141 May 28, 2016
 #3
avatar+118651 
0

Nice answer Geno :)

 May 30, 2016

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