The image of the interval [ -1,3] under the mapping f(x)= 4x³ - 12x is -???

 

Ans- [-8,72]

Please explain me the question and provide answer wid solution.

Don't worry about the rates.

This is the solution. I am taking g=10m/s^2.

 

Ei=mgh=mg5sin37=60

Ef=1/2 k x^2=k/50                                                       (x=0.2)

Change in energy=work done by external force               (which is friction here)

 

so, k/50 - 60 = -mu mg 5cos37

      k/50 - 60= -80 mu --------------------------------------------(1)

 

Now while going up-

Ei=1/2 k x^2 = k/50

Ef= mgh= mg 1 sin37 = 12

 

Therefore, 12 - k/50 = -mu.mg.1.cos37

               12 - k/50= - 16mu -------------------------------------(2)

 

On solving (1), (2), we get mu=0.5

put it in any one of the 2 equations, we get k=1000

 

 

Rate if satisfied. Nudge me if not understood.

Anybody who has given FIITJEE's test series, please tell me how is it? How are the questions? I have heard that some of them are of olympiad level and unsolvable. Is it true?

Please Please tell me something about this.