question 6 solve please
Answers
3 is the answer for 6 question
Answer:
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f(x)=x5−5x4+5x3−1
Differentiating w.r.t x we get,
f′(x)=5x4−20x3+15x2
f′(x)=5x2(x2−4x+3)
when f′(x)=0
⇒5x2(x2−4x+3)=0
⇒5x2(x−3)(x−1)=0
⇒x=0,x=3,x=1
Step 2
Difficult f′(x) again w.r.t x
f′′(x)=20x3−60x2+30x
when x=0;f′′(x)=0
Step 3
when x=3
f′′(x)=20(3)3−60(3)2+30(3)
=540−540+90
⇒f′′(x)>0
Hence x=3 is a point of local minimum.
Step 4
When x=1
f′′(x)=20(1)3−60(1)2+30(1)
=20−60+30
=−10
⇒f′′(x)<0
hence x=1 is the point of local maximum.
Step 5
Substituting x=3 in f(x) we get
f(3)=35−5(3)4+5(3)3−1
=243−405+135−1
=−28
f(1)=15−5(1)4+5(1)3−1
=1−5+5−1
=0
Hence local maximum =0
local minimum =−28
x=0 is the point of inflection.