Examples with solutions for Solving Trinomials: Third power

Exercise #1

3x310x2+7x=0 3x^3-10x^2+7x=0

Video Solution

Step-by-Step Solution

To solve the problem 3x310x2+7x=0 3x^3 - 10x^2 + 7x = 0 , follow these steps:

  • Step 1: Factor out the greatest common factor (GCF). The common factor in all terms is x x . Factoring out x x gives:

x(3x210x+7)=0 x(3x^2 - 10x + 7) = 0

  • Step 2: Apply the Zero Product Property. Set each factor equal to zero:

x=0 x = 0 or 3x210x+7=0 3x^2 - 10x + 7 = 0

  • Step 3: Solve the quadratic equation 3x210x+7=0 3x^2 - 10x + 7 = 0 using the quadratic formula:

The quadratic formula is x=b±b24ac2a x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} . Here, a=3 a = 3 , b=10 b = -10 , c=7 c = 7 .

Calculate the discriminant:

b24ac=(10)24(3)(7)=10084=16 b^2 - 4ac = (-10)^2 - 4(3)(7) = 100 - 84 = 16

Since the discriminant is a perfect square, this quadratic has rational roots. Using the quadratic formula gives:

x=(10)±166=10±46 x = \frac{-(-10) \pm \sqrt{16}}{6} = \frac{10 \pm 4}{6}

Thus, the solutions are:

x=10+46=146=73 x = \frac{10 + 4}{6} = \frac{14}{6} = \frac{7}{3}

x=1046=66=1 x = \frac{10 - 4}{6} = \frac{6}{6} = 1

  • Step 4: Combine all solutions. The solutions to the original equation are:

x=0 x = 0 , x=1 x = 1 , and x=73 x = \frac{7}{3} .

Therefore, the solution to the problem is x=0,1,73 x = 0, 1, \frac{7}{3} .

Answer

x=0,1,73 x=0,1,\frac{7}{3}

Exercise #2

x3+x212x=0 x^3+x^2-12x=0

Video Solution

Step-by-Step Solution

To solve the equation x3+x212x=0 x^3 + x^2 - 12x = 0 , follow these steps:

  • Step 1: Factor out the greatest common factor. The common factor here is x x .
  • Step 2: The equation becomes x(x2+x12)=0 x(x^2 + x - 12) = 0 .
  • Step 3: Apply the zero-product property. This gives us two equations to solve: x=0 x = 0 and x2+x12=0 x^2 + x - 12 = 0 .
  • Step 4: Solve x=0 x = 0 . This is a straightforward solution: x=0 x = 0 .
  • Step 5: Solve the quadratic equation x2+x12=0 x^2 + x - 12 = 0 . We will factor it:
    • Factor as (x3)(x+4)=0 (x - 3)(x + 4) = 0 .
    • Set each factor equal to zero: x3=0 x - 3 = 0 or x+4=0 x + 4 = 0 .
    • Solving these, we obtain x=3 x = 3 and x=4 x = -4 .

Therefore, the solutions to the equation are x=0 x = 0 , x=3 x = 3 , and x=4 x = -4 .

Thus, the complete solution set for x x is x=0,3,4 x = 0, 3, -4 .

Answer

x=0,3,4 x=0,3,-4

Exercise #3

x37x2+6x=0 x^3-7x^2+6x=0

Video Solution

Step-by-Step Solution

To solve the given cubic equation x37x2+6x=0 x^3 - 7x^2 + 6x = 0 , follow these steps:

  • Step 1: Identify that the equation can be factored by its Greatest Common Factor (GCF).

There is an x x common in all terms: x(x27x+6)=0 x(x^2 - 7x + 6) = 0

  • Step 2: Factor the quadratic expression x27x+6 x^2 - 7x + 6 .

Look for two numbers that multiply to 6 6 (the constant term) and add up to 7 -7 (the coefficient of the linear term). The numbers are 1 -1 and 6 -6 . Thus:

x27x+6=(x1)(x6) x^2 - 7x + 6 = (x - 1)(x - 6)

  • Step 3: Set each factor equal to zero to solve for x x .

Now that the equation is fully factored as x(x1)(x6)=0 x(x - 1)(x - 6) = 0 , apply the zero product property:

x=0 x = 0 , x1=0 x - 1 = 0 (so x=1 x = 1 ), x6=0 x - 6 = 0 (so x=6 x = 6 )

Thus, the solutions to the equation x37x2+6x=0 x^3 - 7x^2 + 6x = 0 are x=0 x = 0 , x=1 x = 1 , and x=6 x = 6 .

Answer

x=0,1,6 x=0,1,6