Algebra Questions

Multiple choice
  1. $a+b+c$
  2. $2a+b+c$
  3. $3abc$
  4. $ab+bc+ca$
  5. $abc$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Expanding the equation gives 3x^2 - 2(a+b+c)x + (ab+bc+ca) = 0. For equal roots, the discriminant D = 0. So, 4(a+b+c)^2 - 4*3*(ab+bc+ca) = 0, which simplifies to a^2+b^2+c^2 - ab - bc - ca = 0. This implies a=b=c, meaning a^2+b^2+c^2 = ab+bc+ca.

Multiple choice
  1. $2{ x }^{ 2 }+x-1=0$
  2. $2{ x }^{ 2 }-2x-1=0$
  3. $2{ x }^{ 2 }+2x+1=0$
  4. $2{ x }^{ 2 }+x+1=0$
  5. $2{ x }^{ 2 }+2x-1=0$
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

The root is 1/(1+sqrt(3)). Rationalizing the denominator gives (sqrt(3)-1)/(3-1) = (sqrt(3)-1)/2. If x = (sqrt(3)-1)/2, then 2x + 1 = sqrt(3). Squaring both sides: (2x+1)^2 = 3, so 4x^2 + 4x + 1 = 3, which simplifies to 4x^2 + 4x - 2 = 0, or 2x^2 + 2x - 1 = 0.

Multiple choice
  1. $4x^2 + 5x + 1 = 0$
  2. $4x^2 - x + 1 = 0$
  3. $4x^2 - 5x - 1 = 0$
  4. $4x^2 - 5x + 1 = 0$
  5. $4x^2 + 5x - 1 = 0$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let roots of 2x^2 + 3x + 1 = 0 be a, b. a+b = -3/2, ab = 1/2. We want an equation with roots a^2, b^2. Sum = a^2+b^2 = (a+b)^2 - 2ab = 9/4 - 1 = 5/4. Product = a^2b^2 = (ab)^2 = 1/4. Equation: x^2 - (5/4)x + 1/4 = 0, or 4x^2 - 5x + 1 = 0.

Multiple choice
  1. $-3, -2$
  2. $-3, 2$
  3. $1, -4$
  4. $-5, 1$
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

For x^2 + px + c = 0, roots are 2, -2, so c = product = -4. For x^2 + bx + q = 0, roots are -1, -2, so b = -(sum) = 3. The equation x^2 + bx + c = 0 becomes x^2 + 3x - 4 = 0. Factoring gives (x+4)(x-1) = 0, so roots are -4, 1.

Multiple choice
  1. $\dfrac {1}{14}$
  2. $\dfrac {1}{15}$
  3. $\dfrac {1}{16}$
  4. $\dfrac {1}{17}$
  5. $\dfrac {1}{18}$
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Given a^2 - 3a + 1 = 0, we have a + 1/a = 3. Dividing the numerator and denominator of the expression by a^3 gives 1 / (a^3 + 1/a^3). Using the identity a^3 + 1/a^3 = (a + 1/a)^3 - 3(a + 1/a), we get 3^3 - 3(3) = 27 - 9 = 18, so the value is 1/18.