Let S be the set of positive integral values of a for which a x 2 + 2 a + 1 x + 9 a + 4 x 2 - 8 x + 32 <…

Let S be the set of positive integral values of a for which ax2+2a+1x+9a+4x2-8x+32<0, x. Then, the number of elements in S is:
  1. 1
  2. 0
  3. 3

Solution

Given:

 ax2+2(a+1)x+9a+4x2-8x+32<0  xR

For quadratic x2-8x+32=0,  D1=-82-432=-64

Since the discriminant is less than zero and the leading coefficient is positive, this quadratic will always be positive.

Now, solving ax2+2(a+1)x+9a+4<0

We know that, for a quadratic to be always negative, the coefficient of x2<0, D<0.

a<0 

But we want positive values.

So, no positive integral value exist.

Asked in: JEE Main 2024 (31 Jan Shift 1)

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