Math Problem Statement

Completing the square method. (a) 2x=1-3x²

Solution

To solve the quadratic equation 2x=13x22x = 1 - 3x^2 using the method of completing the square, follow these steps:

Step 1: Rearrange the equation

First, rearrange the equation so that all terms are on one side, leaving zero on the other side.

3x2+2x1=03x^2 + 2x - 1 = 0

Step 2: Normalize the quadratic term

To complete the square, the coefficient of x2x^2 should be 1. Here, it is 3, so divide the entire equation by 3.

x2+23x13=0x^2 + \frac{2}{3}x - \frac{1}{3} = 0

Step 3: Move the constant term to the other side

Move the constant term to the right side of the equation.

x2+23x=13x^2 + \frac{2}{3}x = \frac{1}{3}

Step 4: Complete the square

To complete the square, add and subtract the square of half the coefficient of xx to the left side.

The coefficient of xx is 23\frac{2}{3}. Half of it is 13\frac{1}{3}, and squaring this gives 19\frac{1}{9}.

Add and subtract 19\frac{1}{9} to the left side.

x2+23x+1919=13x^2 + \frac{2}{3}x + \frac{1}{9} - \frac{1}{9} = \frac{1}{3}

This simplifies to:

(x+13)219=13\left(x + \frac{1}{3}\right)^2 - \frac{1}{9} = \frac{1}{3}

Step 5: Isolate the square term

Move 19-\frac{1}{9} to the right side of the equation.

(x+13)2=13+19\left(x + \frac{1}{3}\right)^2 = \frac{1}{3} + \frac{1}{9}

Step 6: Simplify the right side

To simplify the right side, find a common denominator.

13+19=39+19=49\frac{1}{3} + \frac{1}{9} = \frac{3}{9} + \frac{1}{9} = \frac{4}{9}

So, the equation becomes:

(x+13)2=49\left(x + \frac{1}{3}\right)^2 = \frac{4}{9}

Step 7: Solve for xx

Take the square root of both sides.

x+13=±23x + \frac{1}{3} = \pm \frac{2}{3}

Step 8: Isolate xx

Solve for xx by subtracting 13\frac{1}{3} from both sides.

x=13±23x = -\frac{1}{3} \pm \frac{2}{3}

This gives two solutions:

x=13orx=1x = \frac{1}{3} \quad \text{or} \quad x = -1

Final Answer:

The solutions to the equation are:

x=13orx=1x = \frac{1}{3} \quad \text{or} \quad x = -1

Would you like more details or have any questions?

Related Questions:

  1. How can completing the square be used to derive the quadratic formula?
  2. What is the geometrical interpretation of completing the square?
  3. How does completing the square help in finding the vertex of a parabola?
  4. Can you solve a quadratic equation using the quadratic formula and compare it with completing the square?
  5. How do you complete the square for an equation with complex coefficients?

Tip: Completing the square is a powerful tool not just for solving quadratics, but also for rewriting expressions in a form that reveals properties like the vertex of a parabola.

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Math Problem Analysis

Mathematical Concepts

Algebra
Quadratic Equations
Completing the Square

Formulas

Standard form of a quadratic equation: ax^2 + bx + c = 0
Completing the square formula: (x + p)^2 = q
Quadratic equation solutions: x = (-b ± √(b^2 - 4ac)) / 2a

Theorems

Quadratic Formula
Properties of Squares

Suitable Grade Level

Grades 9-10