Calculus basic

Let f:R→R be a differentiable function such that f(x)=x2+e-x∫01 et f(t) dt

q1 f(x) increases in ?
q2 Value of ∫01 f(x) dx

10 Answers

1
Manmay kumar Mohanty ·

for Q1) differentiate using lebnitz theorem ....

62
Lokesh Verma ·

The is is not a very difficult question, and there is no use of lebnitz either....

The integral given there is a constant..

So you an treat the equation as f(x)=x2+cex

Now we have to integrate from 0 to 1

so integral of f(x) from 0 to 1 will be (x^3/3+ce^x)|_0^1=1/3+ce-c

Where c itself is equal to this integral....

Thus, c=1/3+ce-c

So, c(e-2)=-1/3

so c=1/[3(2-e)]

1
nikunj ·

But answers are
ans1 x<-2
ans2 5/12

23
qwerty ·

nishant sir it is e-x and not exso\;f(x)=x^{2}+ce^{-x}

23
qwerty ·

and sir ,
c=\int_{0}^{1}{e^{t}f(t)dt}

but in the sixth line of ur solution u mentioned that c=\int_{0}^{1}{f(t)dt}

62
Lokesh Verma ·

The is is not a very difficult question, and there is no use of lebnitz either....

The integral given there is a constant..

So you an treat the equation as f(x)=x2+ce-x

Now, we have to integrate f(x).ex

which will be easy to do..

Please correct the mistakes from my previous post as given by Qwerty [3]

1
student ·

hmm i tried using that

we get
e=2 !

23
qwerty ·

yes rpf , c gets cancelled on both sides , leaving e = 2 [2] donno how

62
Lokesh Verma ·

\\f(x)=x^2+e^{-x}\int_0^1e^t.f(t)dt \\Let\ c=\int_0^1e^t.f(t)dt \\f(x)=x^2+ce^{-x} \\Let\ c=\int_0^1(e^t.(t^2+ce^{-t}))dt \\\Rightarrow c=\int_0^1(t^2.e^t+c)dt \\\Rightarrow c=\int_0^1(t^2.e^t)dt+c

Yup, you are all correct.. This question has an issue because as you can see that the integral of a +Ve number is zero...

I am sure there is some typing mistake in the problem...
The fact is that such a function cannot exist....

So the question I think is not well prepared..

1
nikunj ·

Thanks everyone [123]

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