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JEE Main
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Mathematics
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Basics of Mathematics

JEE Main · Mathematics · Basics of Mathematics

The number of integral values of a for which the inequality 3 - |x...

The number of integral values of a for which the inequality 3−∣x−a∣>x23 - \left|x - a\right| > x^{2} is satisfied by atleast one negative x, must be equal to

Options

  1. A44
  2. B55
  3. C77
  4. D66

Correct answer

D. 66

Step-by-step solution

Given inequality is
3 - \left|x - a\right| > x^{2} . . . \left(1\right)</p><p></p><p>⇒ \left|x - a\right| < 3 - x^{2}</p><p>or </p><p>or~- 3 + x^{2} < x - a < \left(3 - x^{2}\right)</p><p>or</p><p>orx^{2} - x + a - 3 < 0 \left(2\right)</p><p>and </p><p>and~x^{2} + x - \left(a + 3\right) < 0 . . . \left(3\right)</p><p>If </p><p>If~\alpha,\beta \left(\alpha< \beta\right)betherealandunequalrootsofthecorrespondingequationofEq.(1)be the real and unequal roots of the corresponding equation of Eq. \left(1\right)~for all x \in \left(\alpha,\beta\right).Since Eq. \left(1\right) willhaveatleastonenegativesolution.Thecorrespondingequationof(2)~will have at least one negative solution. The corresponding equation of \left(2\right)~and \left(3\right) are</p><p>~are</p><p>x^{2} - x + a - 3 = 0 . . . \left(4\right)

and~x^{2} + x - \left(a + 3\right) = 0 . . . \left(5\right)<br/>respectively.</p><p>BothEqs.(4)<br />respectively.</p><p>Both Eqs. \left(4\right)~and \left(5\right)~should have real and unequal roots, then

1−41 - 4\cdot11\cdot \left(a - 3\right) > 0 & 1 + 4 \cdot \left(a + 3\right) > 0</p><p>i.e., </p><p>i.e.,~a - \dfrac{13}{4} . . . \left(6\right)</p><p>RootsofEq.(6)</p><p>Roots of Eq. \left(6\right)~are~1±(13−4a)2\dfrac{1 \pm \sqrt{\left(13 - 4a\right)}}{2}

One of these will be negative provided the condition below

13−4a>113 - 4a > 1

i.e.,~a < 3 . . . \left(7\right)</p><p>So,ithasonenegativeroot.</p><p>CombiningEqs.(6)</p><p>So, it has one negative root.</p><p>Combining Eqs. \left(6\right)~and \left(7\right), we get

−-\dfrac{13}{4}<a<3< a < 3

∴∴~Integral values of a are~ −3,−2,−1,0,1,2.- 3, - 2, - 1, 0, 1, 2 .

Total number~=6.= 6 .

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