Q.

Let f(x)=0x2t28t+15etdt, xR. Then the numbers of local maximum and local minimum points of f, respectively, are :           [2025]

1 2 and 3  
2 3 and 2  
3 2 and 2  
4 1 and 3  

Ans.

(1)

From Leibnitz theorem,

f'(x)=(x48x2+15ex2)(2x)

=(x23)(x25)(2x)ex2

=(x3)(x+3)(x5)(x+5)2xex2

 f'(x)=0  x=±3,0,±5

Maxima at x{3,3}

Minima at x{5,0,5}

Hence, 2 points of maxima and 3 points of minima.