vikas askiitian expert
Last Activity: 14 Years ago
step -1
find the deriavative of function= df(x)/dx
step-2
put df(x)/dx=0
let the sol are x=-1 ,4
step-3
now take any number in between -1 to -infinity ,say 0 then if df(x)/dx at x=o is -ve then function is decreasing and if value is +ve then function is increasing in this interval.....
eg..
f(x) = x^3-3x+1
d f(x)/dx =3x^2-3
put df(x)/dx=0
x=(-1,1)
at x =-2 ,df(x)/dx=+ve
at x=0 ,df(x)/dx=-ve
at x=2 ,df(x)/dx=+ve
interval in which function increasing is (-infinity,-1)U(1,+infinity)
interval in which function is decreasing is (-1,+1)
approve my ans if u like