Algebra Questions

Multiple choice
  1. $\displaystyle \frac{(a + b + c)^2 (b^2 - 4ac)}{a^4}$
  2. $\displaystyle \frac{(a + b + c)^2 (b^2 - 4ac)}{a^2}$
  3. $\displaystyle \frac{(a + b + c)^2 (b^2 +4ac)}{a^2}$
  4. $\displaystyle \frac{(a + b + c)^2 (b^2 + 4ac)}{a^4}$
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The determinant represents the product of the Vandermonde-like structure related to the roots. Using the properties of symmetric sums of roots for ax^2 + bx + c = 0, the result simplifies to the discriminant form scaled by the leading coefficient.

Multiple choice
  1. $\dfrac { 3 } { 2 }$
  2. $\dfrac { 1 } { 4 }$
  3. $\dfrac { 1 } { 24 }$
  4. $\dfrac { 1 } { 5 }$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Using L'Hopital's rule or rationalization: Let f(x) = sqrt(1+sqrt(1+x)). The derivative f'(x) = [1/(2*sqrt(1+sqrt(1+x)))] * [1/(2*sqrt(1+x))]. At x=8, f'(8) = [1/(2*sqrt(1+3))] * [1/(2*sqrt(9))] = [1/(2*2)] * [1/(2*3)] = 1/4 * 1/6 = 1/24.

Multiple choice
  1. $\displaystyle a>0$ & $m>1$
  2. $\displaystyle a<0$ & $m<1$
  3. $\displaystyle a<0$ & $\alpha < m < \beta$
  4. $\displaystyle \frac{|a|}{a}=1$ & $m>\alpha$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The limit of |f(x)|/f(x) is 1 if f(x) > 0. For the quadratic ax^2+bx+c to be positive between its roots alpha and beta, the parabola must open downwards (a < 0). Thus, if alpha < m < beta and a < 0, the expression is positive.

Multiple choice
  1. $\displaystyle \frac {2^{n-1}(n-2)+1}{2^n-1}$
  2. $\displaystyle \frac {2^{n}(n-2)+1}{2^n-1}$
  3. $\displaystyle \frac {2^{n-1}(n-1)-1}{2^n-1}$
  4. none of these

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

Let distance be D. Time at 50 kmph is D/50. Time at 60 kmph is D/60. Difference is 15 minutes (10 late to 5 early = 15 min = 0.25 hours). D/50 - D/60 = 0.25. (6D - 5D)/300 = 0.25. D/300 = 0.25. D = 75 km.

Multiple choice
  1. $2 + \sqrt 3 ,2 - \sqrt 3 $
  2. $4 + \sqrt {15} ,4 - \sqrt {15} $
  3. $8 + \sqrt {63} ,8 - \sqrt {63} $
  4. $6 + \sqrt {35} ,6 - \sqrt {35} $
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

If the product of two roots is 1, let the roots be a and 1/a. Using Vieta's formulas for a quintic x^5 - 209x + 56 = 0, the product of all roots is -56. The roots are of the form (a, 1/a, r1, r2, r3). Testing the options, 2+sqrt(3) and 2-sqrt(3) have a product of 4-3=1. Checking if they satisfy the equation confirms they are roots.