The number of integral values of m for which the quadratic expression 1 + 2 m   x 2 - 2 1 + 3 m x + 4 1…

The number of integral values of m for which the quadratic expression 1+2m x2-21+3mx+41+m, xR is always positive, is
  1. 7
  2. 3
  3. 6
  4. 8

Solution

Quadratic expression is positive, hence 1+2m>0 and D<0

m>-12 and

41+3m2-16 1+m1+2m<0

9m2+1+6m-42m2+3m+1<0

m2-6m-3<0

m-3+23m-3-23<0

m3-23, 3+23

m=0, 1, 2, 3, 4, 5, 6

 Number of integral values =7

Asked in: JEE Main 2019 (12 Jan Shift 2)

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