Home
Class 11
MATHS
If alpha,beta are the roots of the equat...

If `alpha,beta` are the roots of the equation `lamda(x^(2)-x)+x+5=0` and if `lamda_(1) and lamda_(2)` are two values of `lamda` obtained from `(alpha)/(beta)+(beta)/(alpha)=4`, then `(lamda_(1))/(lamda_(2)^(2))+(lamda_(2))/(lamda_(1)^(2))` equals.

A

4192

B

4144

C

4096

D

4048

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem step by step, we will follow the reasoning provided in the video transcript. ### Step 1: Rewrite the given quadratic equation The given equation is: \[ \lambda (x^2 - x) + x + 5 = 0 \] This can be rewritten as: \[ \lambda x^2 - \lambda x + x + 5 = 0 \] which simplifies to: \[ \lambda x^2 + (1 - \lambda)x + 5 = 0 \] ### Step 2: Identify coefficients From the quadratic equation \(ax^2 + bx + c = 0\), we have: - \(a = \lambda\) - \(b = 1 - \lambda\) - \(c = 5\) ### Step 3: Use Vieta's formulas According to Vieta's formulas: - The sum of the roots \(\alpha + \beta = -\frac{b}{a} = -\frac{1 - \lambda}{\lambda}\) - The product of the roots \(\alpha \beta = \frac{c}{a} = \frac{5}{\lambda}\) ### Step 4: Use the given condition We are given that: \[ \frac{\alpha}{\beta} + \frac{\beta}{\alpha} = 4 \] This can be rewritten as: \[ \frac{\alpha^2 + \beta^2}{\alpha \beta} = 4 \] Using the identity \(\alpha^2 + \beta^2 = (\alpha + \beta)^2 - 2\alpha \beta\), we substitute: \[ \frac{(\alpha + \beta)^2 - 2\alpha \beta}{\alpha \beta} = 4 \] Substituting the values from Vieta's: \[ \frac{\left(-\frac{1 - \lambda}{\lambda}\right)^2 - 2\left(\frac{5}{\lambda}\right)}{\frac{5}{\lambda}} = 4 \] ### Step 5: Simplify the equation This simplifies to: \[ \frac{\frac{(1 - \lambda)^2}{\lambda^2} - \frac{10}{\lambda}}{\frac{5}{\lambda}} = 4 \] Multiplying through by \(\frac{5}{\lambda}\): \[ \frac{(1 - \lambda)^2}{\lambda^2} - \frac{10}{\lambda} = 20 \] Rearranging gives: \[ \frac{(1 - \lambda)^2}{\lambda^2} = 20 + \frac{10}{\lambda} \] Multiplying through by \(\lambda^2\): \[ (1 - \lambda)^2 = 20\lambda^2 + 10\lambda \] ### Step 6: Expand and rearrange Expanding the left side: \[ 1 - 2\lambda + \lambda^2 = 20\lambda^2 + 10\lambda \] Rearranging gives: \[ \lambda^2 - 22\lambda + 1 = 0 \] ### Step 7: Find the roots \(\lambda_1\) and \(\lambda_2\) Using the quadratic formula: \[ \lambda = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} = \frac{22 \pm \sqrt{(-22)^2 - 4 \cdot 1 \cdot 1}}{2 \cdot 1} \] Calculating the discriminant: \[ \sqrt{484 - 4} = \sqrt{480} = 4\sqrt{30} \] Thus: \[ \lambda_{1,2} = \frac{22 \pm 4\sqrt{30}}{2} = 11 \pm 2\sqrt{30} \] ### Step 8: Calculate \(\frac{\lambda_1}{\lambda_2^2} + \frac{\lambda_2}{\lambda_1^2}\) Let \(\lambda_1 = 11 + 2\sqrt{30}\) and \(\lambda_2 = 11 - 2\sqrt{30}\). We need to find: \[ \frac{\lambda_1}{\lambda_2^2} + \frac{\lambda_2}{\lambda_1^2} \] Using the identity: \[ \frac{a}{b^2} + \frac{b}{a^2} = \frac{a^3 + b^3}{a^2b^2} \] where \(a = \lambda_1\) and \(b = \lambda_2\): \[ \lambda_1^3 + \lambda_2^3 = (\lambda_1 + \lambda_2)(\lambda_1^2 - \lambda_1\lambda_2 + \lambda_2^2) \] Calculating: - \(\lambda_1 + \lambda_2 = 22\) - \(\lambda_1 \lambda_2 = 1\) - \(\lambda_1^2 + \lambda_2^2 = (\lambda_1 + \lambda_2)^2 - 2\lambda_1\lambda_2 = 484 - 2 = 482\) Thus: \[ \lambda_1^3 + \lambda_2^3 = 22(482 - 1) = 22 \times 481 = 10682 \] ### Step 9: Calculate \(\lambda_1^2 \lambda_2^2\) \[ \lambda_1^2 \lambda_2^2 = (\lambda_1 \lambda_2)^2 = 1^2 = 1 \] ### Step 10: Final Calculation Now substituting back: \[ \frac{\lambda_1^3 + \lambda_2^3}{\lambda_1^2 \lambda_2^2} = \frac{10682}{1} = 10682 \] Thus, the final answer is: \[ \boxed{10682} \]
Promotional Banner

Topper's Solved these Questions

  • QUADRATIC EQUATIONS

    ICSE|Exercise EXERCISE 10 (f)|9 Videos
  • PROPERTIES OF TRIANGLE

    ICSE|Exercise EXERCISE 7|38 Videos
  • RELATION AND FUNCTIONS

    ICSE|Exercise MULTIPLE CHOICE QUESTIONS (Choose the correct answer from the given four options in questions)|32 Videos

Similar Questions

Explore conceptually related problems

If alpha, beta are the roots fo the equation lamda(x^(2)-x)+x+5=0 . If lamda_(1) and lamda_(2) are two values of lamda for which the roots alpha, beta are related by (alpha)/(beta)+(beta)/(alpha)=4/5 find the value of (lamda_(1))/(lamda_(2))+(lamda_(2))/(lamda_(1))

Roots of the equation (x^2-4x+3)+lamda(x^2-6x+8)=0 , lamda in R will be

The equation cos ^(2) x - sin x+lamda = 0, x in (0, pi//2) has roots then value(s) of lamda can be equal to :

Let alpha, beta be two real roots of the equation cot ^ 2 x - 2 lamda cot x + 3 = 0 , lamda in R . If cot ( alpha + beta ) = (1)/(2) , then value of lamda is :

Let alpha, beta be two real roots of the equation cot ^ 2 x - 2 lamda cot x + 3 = 0 , lamda in R . If cot ( alpha + beta ) = (1)/(2) , then value of lamda is :

If lamda_(K_(alpha)),lamda_(K_(beta)) and lamda_(L_(alpha)) are the wavelengths of K_(alpha),K_(beta) and L_(alpha) lines, then

If lamda_1 " and " lamda_2 are the wavelengths of the first members of the Lyman and paschen series respectively, then lamda_1/lamda_2 is equal to

If equation (lamda^(2)-5lamda+6)x^(2)+(lamda^(2)-3lamda+2)x+(lamda^(2)-4)=0 is satisfied by more than two values of x , find the parameter lamda .

If sin alpha = lamda sin (theta - alpha ) then prove that tan (alpha - (theta)/(2)) = (lamda -1)/( lamda +1) tan ""(theta)/(2).

Find the values of lamda and mu if both the roots of the equation (3lamda+1)x^(2)=(2lamda+3mu)x-3 are infinite.

ICSE-QUADRATIC EQUATIONS-CHAPTER TEST
  1. For what values of m will the equation x^(2)-2mx+7m-12=0 have (i) equa...

    Text Solution

    |

  2. If one root of 2x^(2)-5x+k=0 be double the other, find the value of k.

    Text Solution

    |

  3. If alpha,beta be the roots of the equation x^(2)-x-1=0, determine the ...

    Text Solution

    |

  4. If the roots of the equation ax^(2)+bx+c=0 be in the ratio 3:4, show t...

    Text Solution

    |

  5. If x is real, prove that the quadratic expression (i) (x-2)(x+3)+7 is ...

    Text Solution

    |

  6. Draw the graph of the quadratic function x^(2)-4x+3 and hence find the...

    Text Solution

    |

  7. For what real values of a, will the expression x^(2)-ax+1-2a^(2), for ...

    Text Solution

    |

  8. If x be real, prove that the value of (2x^(2)-2x+4)/(x^(2)-4x+3) canno...

    Text Solution

    |

  9. If the roots of the equation qx^(2)+2px+2q=0 are real and unequal, pro...

    Text Solution

    |

  10. If alpha,beta be the roots of x^(2)-px+q=0, find the value of alpha^(5...

    Text Solution

    |

  11. If the difference between the roots of the equation x^(2)+ax+1=0 is le...

    Text Solution

    |

  12. Let alpha,beta be the roots of the equation x^(2)-px+r=0 and alpha//2,...

    Text Solution

    |

  13. alpha,beta are the roots of ax^(2)+2bx+c=0 and alpha+delta,beta+delta ...

    Text Solution

    |

  14. If alpha,beta are the roots of the equation x^(2)-2x-1=0, then what is...

    Text Solution

    |

  15. If the roots of the quadratic equation x^(2)+px+q=0 are tan 30^(@) and...

    Text Solution

    |

  16. If both the roots of the quadratic equation x^(2)-2kx+k^(2)+k-5=0 are ...

    Text Solution

    |

  17. If alpha and beta are the roots of ax^(2)+bx+c=0 and if px^(2)+qx+r=0...

    Text Solution

    |

  18. The quadratic equations x^(2)-6x+a=0 and x^(2)-cx+6=0 have one root in...

    Text Solution

    |

  19. If alpha,beta are the roots of the equation lamda(x^(2)-x)+x+5=0 and i...

    Text Solution

    |

  20. If alpha,beta be the roots of x^(2)-a(x-1)+b=0, then the value of (1)/...

    Text Solution

    |