Multiple choice

If $\alpha$ and $\beta$ are the roots of the equation $x^2-3x-1=0$, then form a quadratic equation whose roots are$\dfrac{1}{\alpha^2} $ and $\dfrac{1}{\beta^2}$.

  1. $x^2-11x+1=0$
  2. $x^2+11x+1=0$
  3. $x^2-11x-1=0$
  4. None of these

Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

For x^2-3x-1=0, sum of roots alpha+beta = 3 and product alpha*beta = -1. The new roots are 1/alpha^2 and 1/beta^2. Their sum is (alpha^2+beta^2)/(alpha*beta)^2 = ((alpha+beta)^2 - 2alpha*beta)/(alpha*beta)^2 = (9+2)/1 = 11. Their product is 1/(alpha*beta)^2 = 1/1 = 1. The equation is x^2 - 11x + 1 = 0.

AI explanation

For the equation x^2-3x-1=0, the sum of roots a+b = 3 and the product ab = -1. The new roots are 1/a^2 and 1/b^2, so the new sum is (a^2+b^2)/(a^2*b^2) = ((a+b)^2-2ab)/(ab)^2 = (3^2-2(-1))/(-1)^2 = 11/1 = 11. The new product is 1/(a^2*b^2) = 1/(-1)^2 = 1. The required equation is x^2-11x+1=0.