Can you solve this?

How many ordered pairs of positive integers ( a , b ) (a,b) are there such that

a + b 11 a + 12 b ? a + b | 11a + 12 b ?


The answer is 0.

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3 solutions

U Z
Dec 15, 2014

11 a + 11 b a + b + b a + b \dfrac{11a + 11b}{a + b} + \dfrac{b}{a + b}

11 + 1 a b + 1 11 + \dfrac{1}{\dfrac{a}{b} + 1}

since a , b N a,b \in N , thus when a+b divides it we should get a natural number , now here we can see 1 is not divisible by any natural number rather than 1 . So for the expression to be a natural number , a should be zero, b 0 b \neq 0 , but a , b N a,b \in N .

Thus z e r o \boxed{zero} solutions

A slightly simpler way (equivalent to yours) is to say that we want a + b b a + b | b . But since b < a + b b < a + b , hence there are no solutions.

Calvin Lin Staff - 6 years, 5 months ago
Md Zuhair
Oct 7, 2016

Here a + b 11 a + 12 b a+b|11a+12b . Now a + b 11 a + 11 b + b a+b|11a+11b+b We know a + b 11 a + 11 b a+b|11a+11b . Hence a + b b a+b|b . But a larger number cannot divide a smaller number. Hence there is no solution.

Fox To-ong
Jan 10, 2015

a must be = 0

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