Multiple choice

If the product of the roots of the equation $\displaystyle x^{2}-5x+4^{log_{2}\lambda }=0$ is $8$, then $\lambda $ is

  1. $\pm2\sqrt{2}$
  2. $2\sqrt{2}$
  3. $3$
  4. none of these

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

For x^2 - 5x + 4^(log2(lambda)) = 0, the product of roots is the constant term: 4^(log2(lambda)) = 8. (2^2)^(log2(lambda)) = 2^(2 * log2(lambda)) = 2^(log2(lambda^2)) = lambda^2. So lambda^2 = 8, lambda = sqrt(8) = 2*sqrt(2).

AI explanation

By Vieta's formulas, the product of the roots is the constant term, so we set $4^{\log_{2}\lambda} = 8$. Applying the base change formula to the bases, we rewrite 4 as $2^2$ and 8 as $2^3$, giving $2^{2\log_{2}\lambda} = 2^3$. By the properties of logarithms, this simplifies to $\lambda^2 = 8$. Solving for the positive real value of $\lambda$, we find $\lambda = 2\sqrt{2}$.