Assertion-Reason 1

Let f(x) be a continuous and differential fn.

(A) : There exists a 'c' in [2,6] such that (f(6))2 - (f(2))2 = 8f(c)f '(c)

(R) : By LMVT, f(6) - f(2) = 4f '(c) for some 'c' in [2,6] and
By IVT, f(6) + f(2) = 2f(c) for some 'c' in [2,6].

24 Answers

1
madeforiit ·

y ans B???
bhaiya jus proved IVT part of Reason to be false....

9
Celestine preetham ·

i fore saw that in post no 12 ;)

11
rkrish ·

The answer is B (as mentioned by Celestine)
St. 1- True : take G(x)= F(x)2 and apply LMVT (as mentioned by Celestine)

St. 2-True : (a,b) is used.. but then if applicable in (a,b) it has to also be applicable in a greater set. (as mentioned by Nishant bhaiyya)
how do you justify that the value will hold for the same value of c!! (as mentioned by Nishant bhaiyya)
The 2 c's need not be same.

Hence answer is B.

11
rkrish ·

I am EXTREMELY Sorry.I made a typing error!![2][2][2]

It is By IVT f(6)+f(2)=2f(c) for some 'c' in [2,6]

I am very sorry!! I have made the change.

62
Lokesh Verma ·

@madeforiit.. I have already shown it is not true.

and celestine has given teh condition when it wud work !

9
Celestine preetham ·

made thats wrong

1
madeforiit ·

celestine y r u sayin this is true????

coz as bhaiya said

Take a very simple example when f(x)=1 is the function.. for all x.

f(6)=1 and f(2)=1

then 4. f(c)= 4 for all c

so 4f(c) ≠1+1 for any c in (2,6)

9
Celestine preetham ·

take G(x)= F(x)2 and apply LMVT

1
madeforiit ·

can sum1 prove this : [provided it is rite]

f(6) + f(2) = 4f(c) for some 'c' in [2,6].

62
Lokesh Verma ·

but celestine.. how do you justify that the value will hold for the same value of c!!

there are 2 c's involved?

1
madeforiit ·

@nish bhaiya.... k so if it cums as an assertn reason we must not b concerned abt the [].....

9
Celestine preetham ·

see again ;)

39
Dr.House ·

answer is c ????????????

62
Lokesh Verma ·

in IVT, LMVT

(a,b) is used.. but then if applicable in (a,b) it has to also be applicable in a greater set.

9
Celestine preetham ·

ans is B

if uve wrongly typed
By IVT, f(6) + f(2) = 4f(c) for some 'c' in [2,6].

in place of

By IVT, f(6) + f(2) = 2f(c) for some 'c' in [2,6].

1
madeforiit ·

pl. confirm nish bhaiya

1
madeforiit ·

I hav one fundamental doubt......... In LMVT and IVT while defining range of c....
which of the fol is correct range.....

(a,b) OR [a,b] or is it that both are ok....

1
madeforiit ·

yeah!!! cool....

Is this stat true : f(6) + f(2) = 2f(c) for c belonging (2,6) { IVT}

If yes then stat A can be easily proved
There exists a 'c' in [2,6] such that (f(6))2 - (f(2))2 = 8f(c)f '(c)

jus multiply the 2 statements.... :)

62
Lokesh Verma ·

Take a very simple example when f(x)=1 is the function.. for all x.

f(6)=1 and f(2)=1

then 4. f(c)= 4 for all c

so 4f(c) ≠1+1 for any c in (2,6)

!!!

1
madeforiit ·

que1 y is this stat false : By IVT, f(6) + f(2) = 4f(c) for some 'c' in [2,6]. ????

Q2 wud the stat been rite had it been By IVT, f(6) + f(2) = 4f(c) for some 'c' in (2,6).

62
Lokesh Verma ·

what does your statement mean? sorry i was unable to comprehend it :(

1
madeforiit ·

By IVT, f(6) + f(2) = 4f(c) for some 'c' in [2,6].

this stat is false ne.....

In this functn bcoz we dunno f(2) & f(6) here.....
Can ne be made using IVT???

OR IS JUST THE MISTAKE IN [2,6] which shud b (2,6)??

62
Lokesh Verma ·

I dont C why C should not be the answer..

R is false.. because the 2nd statement is untrue.

By IVT, f(6) + f(2) = 4f(c) for some 'c' in [2,6].

A is true! (I cant think of a proof immediately.. but am sure.. and I think this is a standard often asked question :)

11
rkrish ·

No. Even I thought it to be (C)[2]

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