Sign in
12thPass logo
New chatPYQ LibraryDoubtsRank report
Sign in to see Recents

Your guest activity stays on this device

Sign in to save progress →
Sign in

Quadratic Equation and Inequalities question

2023 · 24 Jan · Shift 2 · Q24
Guest · filters and generic practice availableBrowsing as a guest · PYQ filters and generic practice are available. Sign in only for personalised features and saved progress.
  1. PYQ Library
  2. /JEE Main
  3. /Mathematics
  4. /Quadratic Equation and Inequalities
  5. /2023 · 24 Jan · Shift 2 · Q24

Quadratic Equation and Inequalities question

2023 · 24 Jan · Shift 2 · Q24

JEE MainMathematicsQuadratic Equation and InequalitiesMCQ+4 / −1
The number of real solutions of the equation 3(x2+1x2)−2(x+1x)+5=03\left( {{x^2} + {1 \over {{x^2}}}} \right) - 2\left( {x + {1 \over x}} \right) + 5 = 03(x2+x21​)−2(x+x1​)+5=0, is
  1. A
    3
  2. B
    4
  3. C
    0
  4. D
    2
View written solutionFree

Correct answer: C

  1. Given equation

3(x2+1x2)−2(x+1x)+5=03\left(x^2+\frac{1}{x^2}\right)-2\left(x+\frac{1}{x}\right)+5=03(x2+x21​)−2(x+x1​)+5=0

We need the number of real solutions.

Also note that x≠0x\neq 0x=0 because of the terms 1x\frac1xx1​ and 1x2\frac1{x^2}x21​.


  1. Substitute a standard expression

Let

t=x+1xt=x+\frac{1}{x}t=x+x1​

Then,

x2+1x2=(x+1x)2−2=t2−2x^2+\frac{1}{x^2}=\left(x+\frac{1}{x}\right)^2-2=t^2-2x2+x21​=(x+x1​)2−2=t2−2

Substitute into the equation:

3(t2−2)−2t+5=03(t^2-2)-2t+5=03(t2−2)−2t+5=0

3t2−6−2t+5=03t^2-6-2t+5=03t2−6−2t+5=0

3t2−2t−1=03t^2-2t-1=03t2−2t−1=0


  1. Solve for ttt

3t2−2t−1=03t^2-2t-1=03t2−2t−1=0

Factorizing:

3t2−3t+t−1=03t^2-3t+t-1=03t2−3t+t−1=0

3t(t−1)+1(t−1)=03t(t-1)+1(t-1)=03t(t−1)+1(t−1)=0

(3t+1)(t−1)=0(3t+1)(t-1)=0(3t+1)(t−1)=0

So,

t=1ort=−13t=1 \quad \text{or} \quad t=-\frac13t=1ort=−31​

That is,

x+1x=1orx+1x=−13x+\frac1x=1 \quad \text{or} \quad x+\frac1x=-\frac13x+x1​=1orx+x1​=−31​


  1. Check which values of ttt are possible for real xxx

For real x≠0x\neq 0x=0,

x+1x≥2orx+1x≤−2x+\frac1x\ge 2 \quad \text{or} \quad x+\frac1x\le -2x+x1​≥2orx+x1​≤−2

So the expression x+1xx+\frac1xx+x1​ cannot take any value strictly between −2-2−2 and 222.

But both values obtained are:

  • t=1t=1t=1
  • t=−13t=-\frac13t=−31​

Both lie in the interval (−2,2)(-2,2)(−2,2), so neither is possible for real xxx.

Hence there are no real solutions.


  1. Conclusion

The number of real solutions is

0\boxed{0}0​

So the correct option is C.


  1. Comparison with stored answer

Stored correct answer: C

Our derived answer: C

They agree.

PreviousNext

More from Quadratic Equation and Inequalities

  • Let α∈R and let α,β be the roots of the equation x2+6041​x+a=0. If α4+β4=−30, then the product of all possible values of a is ​.2023 · Numerical
  • Let λe0 be a real number. Let α,β be the roots of the equation 14x2−31x+3λ=0 and α,γ be the roots of the equation 35x2−53x+4λ=0. Then β3α​ and γ4α​…2023 · MCQ
  • Let α1​,α2​,....,α7​ be the roots of the equation x7+3x5−13x3−15x=0 and ∣α1​∣≥∣α2​∣≥...≥∣α7​∣. Then α1​α2​−α3​α4​+α5​α6​ is…2023 · Numerical
  • If the value of real number a>0 for which x2−5ax+1=0 and x2−ax−5=0 have a common real root is 2β​3​ then β is equal to ​.2023 · Numerical
  • The number of real roots of the equation x2−4x+3​+x2−9​=4x2−14x+6​, is :2023 · MCQ
  • The equation e4x+8e3x+13e2x−8ex+1=0,x∈R has :2023 · MCQ
  • If the sum of the squares of the reciprocals of the roots α and β of the equation 3x2 +λ x − 1 = 0 is 15, then 6(α 3 + β 3)2 is equal to :2022 · MCQ
  • The sum of all the real roots of the equation (e2x−4)(6e2x−5ex+1)=0 is2022 · MCQ