IIT JEE , AIEEE Forum - Mathematics , Differential Calculus - try out dis funky question......only for brainys plzz!!!!!!!means 4 all d goiitians lolzz

ishita247

x+x+x+x+x+x+x+x+x................................x times = x²

differentiatin both sides wrt x

1 + 1+1+1+1+1+1+1............................x times = 2x

=> x = 2x

cancellin x

1 = 2

spot the defect in d workin.....................

apurviitjee2008

u have ignored x=0 as the solution

ishita247

dats jus 1 case u can make out

try out other cases

it comes out 1=2

try again

ishita247

nobody tryin!!!

hey brainys buck up!!!

joyfrancis

x+x+x+x....x times = x^2 only when x is an integer...so x becomes a non differentiable function

ishita247

wow joy excellently answered

ya dis fn isnt continuous n wont hold for fractional values

so dis bcums a non differentiable fn............

well done

n ya if u liked d question plzzz rate me for it.............................

cheers

rhd92781

hey ishita, this is such a disgusting sort of mathematics

saying if 1*0=0 and 2*0 = 0 then 1=2.

if u have an equn, 2x-2=0 or x=1
u could well have said 3x-x-3+1=0 of 3(x-1)=x-1 so either x=1 or 1=3. but looking up, the eqn was as simple as x-1=0 or x=1

was'nt that what u were mistaking

the only soln to ur eqn 2x=x is x=0. one more thing, it is a linear eqn, it can't have more than 1 root

joyfrancis

what is so disgusting?...conceptual problems are good..

ishita247

wrong dis question was asked in one of d competitive exams in d mains

n d answer joy gave is d perfect soln to it

d ques itself said find d defect so obviously it had 2 b wrong na

n if u thnk it was disgustin u might as well believe d same for d exam

it wasnt made up by me

but ya d answer was found out by me.............

dats why i posted it here 2 make others also aware of d trick

dont u thnk i deserved a better reply dan wat u gave???

spideyunlimited

aaye joy!!! mujhe bhi fiitjee sir ne yahi puccha tha... !! u too?!
well differentiation is only applicable for continuous small values and not discreet values like integers which exist at specific points. Hence the working is invalid.

ishita247

ya dats rght!!!!

rhd92781

the important thing in the question was to say the non differentiability of the function which is correct.nothing disgusting in that.

the point i was pointing was that saying there r two solutions of the eqn 2x=x, 0 and something else is absurd. i meant if x=2x, it doesn't mean that 1=2

suhaasraj

dat ws a gud one

nishantsingh89

gud one takes u right to the basics :)

Ask & Discuss Questions with Community & Experts