Any of you Math Exxperts out there? Try to solve this.

[tahatehseen]

lets see who can solve this fallacious proof.

if a=b
a^2=ab
(subtract b^2 from both sides)
a^2-b^2=ab-b^2
(a+b)(a-b)=b(a-b)
divide a-b from both sides of the equation
a+b=b
given a=b
b+b=b
2b=b
(divide both sides by b)
2=1

strange? :%) :%) :%) :%) :%) now try to find the fallacy (wrong part) in this proof.

 

[scouserlfc]

its the step in which u divide from (a-b) its wrong as if u replace a with b by the proof in the start a=b then:
( a - b ) equals ( b-b) which will be 0(zero) and the answer will be undefined so its wrong !!

 

[abcde]

^ Exactly!

 

[scouserlfc]

give more of these if this is correct which im sure it is,canu tell me where to get these fallacies !!

 

[tahatehseen]

@scouser..correct!!! i new there are some brainiacs in XPF!!

 

[tahatehseen]

x=0
(multiply both by x-1)
(x)(x-1)=0
(x-1)=0
x=1
1=0
strange again..lets see who does it this time.

 

[abcde]

I think that the conclusion derived in the step x -1 = 0 is incorrect. If x (x -1) = 0 that does not necessarily imply that (x - 1) = 0.
-1 cannot be equal to 0 here obviously!

 

[Silent Hunter]

^^ correct i think

 

[tahatehseen]

abcde is correct..
now this one here

We are going to prove that 2π = 0:

x = 2π
sin(x) = 0
x = arcsin(0)
x = 0
2π = 0

arcsin means sininverse

 

[tahatehseen]

whats the trick here??

 

[OakMoon!]

whats the trick here??

LOL! This fallacy challenges the basic meaning of differentiation. You can't find the derivative with respect to a constant since it's not changing, and in this case it is given that x=1 which is a constant.

 

[princesszahra]

u know what i can confuse the first equation more !!!!!!!!!!

 

[OakMoon!]

You definitely can. Fallacies can be arranged in any way since it doesn't follow the logical reasoning of Mathematics.

Why don't you guys try your mathematics knowledge by proving a true Mathematical expression? That's a more bigger challenge than giving the reasoning behind a false proof which is quite apparent.

 

[scouserlfc]

can u tell where we can get that ???

 

[OakMoon!]

Everywhere! Just type in Mathematical Proof on google, and you'll get a hell lot of proofs. It's just that, in international competitions it's the proofs type questions that they ask so you should practice them out. Maybe, out of the many students here someone gets this part of Mathematics better than someone else and can go on to represent Pakistani team at the International Mathematics Olympiad or the other Olympiads happening out there. Our students are never introduced to this wing of Mathematics at the seondary level which results in our failure at these competitions.

 

[scouserlfc]

yup u are right, i just found out that in the Kangroo Math Competition about 3 months ago it was tough as the maths was not the maths we are familiar with !!

 

[OakMoon!]

Kangaroo is different, what I am talking about is different. Atleast you know what you have to do to solve the questions of Kangaroo Mathematics, if you try you can do them.

 

[AnotherStudent]

@tahatehseen

try finding d/dx(x^(x^x))

 

[OakMoon!]

^This question requires rigorous implicit differentiation after taking natural logarithm on boh sides as you make an equation y=(x^(x^x)).
You get the answer dy/dx=x^(x^x)[x^x(ln x +1)lnx+x^(x-1)]

You can get the solution of this question anywhere on the net. It's a very common differentiation problem.

 

[AnotherStudent]

@hamid ali

i asked this because it a little tricky for any addmath student and i know many others can also do it. i specifically asked tahatehseen as he was asking about very basic things and i wanted to know if he could do that