help with this question? (1 Viewer)

[muttiah]

if u have the cambridge book den page 366 q8.. there is 4 parts....part (d) is the one im having difficulty in

8(a) If f(x) = 3x / x^2+1, show that f'(x) =3(1-x)(1+x) / (x^2+1) [done]

(b) Hence find any stationery points and analyse them [done]

(c) Sketch a graph of y=f(x) [done]

(d)Hence state how many roots the eqn 3x / x^2+1 = c for:
(i)c > 3/2

thanks 4 ur help!

 

[SoulSearcher]

It is basically asking for how many values of x the graph is above the value of 3/2. Looking at the graph, there are no values of x for which c > 3/2 and thus the number of roots is 0.

 

[muttiah]

can u explain it again plz..

are they asking "how many times is the graph f(x) passing the x axis when
c > 3/2"


does it mean y > 3/2 or f(x) > 3/2

thanks bye

 

[SoulSearcher]

y and f(x) are basically the same thing, so it is looking for how many times f(x) goes above 3/2.

 

[muttiah]

kk
so how about this one

0 < c < 3/2

so how amny times does f(x) go thru those points....

how would u do this one

sry for the inconvenience.