Home
Class 11
MATHS
If alpha,beta are the roots of ax^(2)+bx...

If `alpha,beta` are the roots of `ax^(2)+bx+c=0`, form that equation whose roots are `(alpha^(2)+beta^(2)),((1)/(alpha^(2))+(1)/(beta^(2)))`.

Text Solution

AI Generated Solution

The correct Answer is:
To find the quadratic equation whose roots are \( \alpha^2 + \beta^2 \) and \( \frac{1}{\alpha^2} + \frac{1}{\beta^2} \), we will follow these steps: ### Step 1: Find \( \alpha + \beta \) and \( \alpha \beta \) From the given quadratic equation \( ax^2 + bx + c = 0 \), we know: - The sum of the roots \( \alpha + \beta = -\frac{b}{a} \) - The product of the roots \( \alpha \beta = \frac{c}{a} \) ### Step 2: Calculate \( \alpha^2 + \beta^2 \) Using the identity: \[ \alpha^2 + \beta^2 = (\alpha + \beta)^2 - 2\alpha\beta \] Substituting the values we found in Step 1: \[ \alpha^2 + \beta^2 = \left(-\frac{b}{a}\right)^2 - 2\left(\frac{c}{a}\right) \] Calculating this gives: \[ \alpha^2 + \beta^2 = \frac{b^2}{a^2} - \frac{2c}{a} = \frac{b^2 - 2ac}{a^2} \] ### Step 3: Calculate \( \frac{1}{\alpha^2} + \frac{1}{\beta^2} \) Using the identity: \[ \frac{1}{\alpha^2} + \frac{1}{\beta^2} = \frac{\beta^2 + \alpha^2}{\alpha^2 \beta^2} \] Substituting the values we have: \[ \frac{1}{\alpha^2} + \frac{1}{\beta^2} = \frac{\alpha^2 + \beta^2}{\alpha^2 \beta^2} \] We already calculated \( \alpha^2 + \beta^2 \) in Step 2. Now we need \( \alpha^2 \beta^2 \): \[ \alpha^2 \beta^2 = (\alpha \beta)^2 = \left(\frac{c}{a}\right)^2 = \frac{c^2}{a^2} \] Thus, \[ \frac{1}{\alpha^2} + \frac{1}{\beta^2} = \frac{\frac{b^2 - 2ac}{a^2}}{\frac{c^2}{a^2}} = \frac{b^2 - 2ac}{c^2} \] ### Step 4: Find the sum of the new roots Now we can find the sum of the new roots: \[ \text{Sum} = \left(\alpha^2 + \beta^2\right) + \left(\frac{1}{\alpha^2} + \frac{1}{\beta^2}\right) = \frac{b^2 - 2ac}{a^2} + \frac{b^2 - 2ac}{c^2} \] Finding a common denominator: \[ \text{Sum} = \frac{(b^2 - 2ac)c^2 + (b^2 - 2ac)a^2}{a^2c^2} = \frac{(b^2 - 2ac)(a^2 + c^2)}{a^2c^2} \] ### Step 5: Find the product of the new roots Next, we find the product of the new roots: \[ \text{Product} = \left(\alpha^2 + \beta^2\right) \left(\frac{1}{\alpha^2} + \frac{1}{\beta^2}\right) = \left(\frac{b^2 - 2ac}{a^2}\right) \left(\frac{b^2 - 2ac}{c^2}\right) = \frac{(b^2 - 2ac)^2}{a^2c^2} \] ### Step 6: Form the new quadratic equation The new quadratic equation can be formed using the sum and product of the roots: \[ x^2 - \text{(Sum)} \cdot x + \text{(Product)} = 0 \] Substituting the values we found: \[ x^2 - \frac{(b^2 - 2ac)(a^2 + c^2)}{a^2c^2} x + \frac{(b^2 - 2ac)^2}{a^2c^2} = 0 \] ### Final Form Multiplying through by \( a^2c^2 \) to eliminate the denominators gives: \[ a^2c^2x^2 - (b^2 - 2ac)(a^2 + c^2)x + (b^2 - 2ac)^2 = 0 \] This is the required quadratic equation whose roots are \( \alpha^2 + \beta^2 \) and \( \frac{1}{\alpha^2} + \frac{1}{\beta^2} \). ---
Promotional Banner

Topper's Solved these Questions

  • QUADRATIC EQUATIONS

    ICSE|Exercise EXERCISE 10 (a)|11 Videos
  • QUADRATIC EQUATIONS

    ICSE|Exercise EXERCISE 10 (b)|16 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 of x^(2)+2x-1=0 , then the equation whose roots are alpha^(2), beta^(2) is

If alpha, beta are the roots of x^(2)+x+1=0 , then the equation whose roots are alpha^(5), beta^(5) is

If alpha, beta are the roots of ax^2 + bx + c = 0, the equation whose roots are 2 + alpha, 2 + beta is

If alpha and beta are the roots of ax^(2)+bx+c=0 , form the equation whose roots are (1)/(alpha) and (1)/(beta) .

If alpha, beta are the roots of x^(2)-3x+1=0 , then the equation whose roots are (1/(alpha-2),1/(beta-2)) is

If alpha, beta are the roots of x^(2)+6x+9=0 , then the equation whose roots are (1)/(alpha), (1)/(beta) is

If alpha and beta are the roots of the equation x^(2)+x-7=0 , form the equation whose roots are alpha^(2) and beta^(2) .

If alpha, beta are the roots of x^(2)+3x+1=0 , then the equation whose roots 2-alpha, 2-beta is

If alpha, and beta are the roots of x^(2)+px+q=0 form a quadratic equation whose roots are (alpha-beta)^(2) and (alpha+beta)^(2) .

If alpha, beta are the roots of x^(2)+2x+5=0 , then the equation whose roots are (alpha+1)/(alpha), (beta+1)/(beta) is

ICSE-QUADRATIC EQUATIONS-CHAPTER TEST
  1. If alpha,beta are the roots of ax^(2)+bx+c=0, form that equation whose...

    Text Solution

    |

  2. Solve the equation: 5^(x+1)+5^(2-x)=5^(3)+1

    Text Solution

    |

  3. Solve the equations: sqrt((x)/(1-x))+sqrt((1-x)/(x))=(13)/(6).

    Text Solution

    |

  4. Solve the equations: (x+1)(x+2)(x+3)(x+4)=120

    Text Solution

    |

  5. Prove that both the roots of the equation x^(2)-x-3=0 are irrational.

    Text Solution

    |

  6. For what values of m will the equation x^(2)-2mx+7m-12=0 have (i) equa...

    Text Solution

    |

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

    Text Solution

    |

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

    Text Solution

    |

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

    Text Solution

    |

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

    Text Solution

    |

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

    Text Solution

    |

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

    Text Solution

    |

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

    Text Solution

    |

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

    Text Solution

    |

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

    Text Solution

    |

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

    Text Solution

    |

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

    Text Solution

    |

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

    Text Solution

    |

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

    Text Solution

    |

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

    Text Solution

    |

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

    Text Solution

    |