## Search found 21 matches

Sat Mar 23, 2019 3:53 pm
Forum: Secondary Level
Topic: BdMO 2017 Dhaka divitional
Replies: 3
Views: 637

### Re: BdMO 2017 Dhaka divitional

Original solution by Tonmoy. Let $P(x,y)$ be the assertion $f(x+y)=f(x)f(y)-f(xy)+1$ $P(0, 0)$ $\Longrightarrow$ $f(0) = 1$. Claim 1: $f(1) \neq 1$. Proof of claim 1: If $f(1)=1$, then $P(x-1,1)$ $\Longrightarrow$ $f(x)=1$ $\forall x$. But it is given that $f(2017) \neq f(2018)$, a contradiction. C...
Sun Mar 17, 2019 7:49 pm
Topic: BdMO National Higher Secondary 2019/8
Replies: 2
Views: 365

### Re: BdMO National Higher Secondary 2019/8

May be this answer is not correct as the question asked to prove that there exists a subset $S$ such that in $S$ there are infinitely many multiples of any natural number $n$. here you have proven for a natural number $n$ there is a subset which have infinite multiple of $n$. But you have to prove i...
Sat Mar 16, 2019 12:51 am
Topic: BdMO National Higher Secondary 2019/7
Replies: 3
Views: 527

### Re: BdMO National Higher Secondary 2019/7

May be not for all cases $AB=BC$ can't be drawn even if $r_1+r_3\geq 2r_2$. I think $2r_{2}^{2} \geq r_{1}^{2}+r_{3}^{2}$ also must hold
Sun Mar 10, 2019 10:54 pm