Let the function f ( x ) = 2 x 3 + ( 2 p - 7 ) x 2 + 3 ( 2 p - 9 ) x - 6 have a maxima for some value of x…

Let the function f(x)=2x3+(2p-7)x2+3(2p-9)x-6 have a maxima for some value of x<0 and a minima for some value of x>0. Then, the set of all values of p is
  1. 92,
  2. 0,92
  3. -,92
  4. -92,92

Solution

Given,f(x)=2x3+(2p-7)x2+3(2p-9)x-6

On taking differentiation w.r.t x, we get

f'(x)=6x2+2(2p-7)x+3(2p-9)

f'(0)=6(0)2+2(2p-7)(0)+3(2p-9)

f'(0)=3(2p-9)

Here, given that for x<0 the function has maxima and for x>0 the function has minima so the function is decreasing function about x=0,

Hence f'(0)<0

So, 3(2p-9)<0

p<92

Therefore, p-,92

Asked in: JEE Main 2023 (25 Jan Shift 2)

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