Math Problem Statement

Using the quadratic formula, solve 4x^2 + 12x + 5 = 0 to find the two possible values of x. Give any decimal answers to 1 d.p.

Solution

Given the quadratic equation 4x2+12x+5=04x^2 + 12x + 5 = 0, we need to find the two possible values of xx using the quadratic formula:

The quadratic formula is: x=b±b24ac2ax = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}

Here, a=4a = 4, b=12b = 12, and c=5c = 5. Let's plug these values into the formula:

Step 1: Calculate the Discriminant

b24ac=1224×4×5=14480=64b^2 - 4ac = 12^2 - 4 \times 4 \times 5 = 144 - 80 = 64

Step 2: Find the Square Root of the Discriminant

64=8\sqrt{64} = 8

Step 3: Apply the Quadratic Formula

x=12±82×4=12±88x = \frac{-12 \pm 8}{2 \times 4} = \frac{-12 \pm 8}{8}

Step 4: Calculate the Two Possible Values of xx

  1. For the plus sign: x1=12+88=48=0.5x_1 = \frac{-12 + 8}{8} = \frac{-4}{8} = -0.5

  2. For the minus sign: x2=1288=208=2.5x_2 = \frac{-12 - 8}{8} = \frac{-20}{8} = -2.5

Final Answer

The two possible values of xx are: x1=0.5andx2=2.5x_1 = -0.5 \quad \text{and} \quad x_2 = -2.5

Would you like more details, or do you have any questions?

Here are 5 related questions you might find helpful:

  1. How do you know when a quadratic equation has real solutions?
  2. What does the discriminant tell you about the nature of the roots of a quadratic equation?
  3. Can the quadratic formula be used for all quadratic equations?
  4. How do you factorize a quadratic equation when it's factorable?
  5. What are other methods for solving quadratic equations besides the quadratic formula?

Tip: Always check the discriminant (b24acb^2 - 4ac) before using the quadratic formula. It helps you identify the nature of the roots: real or complex.

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Math Problem Analysis

Mathematical Concepts

Quadratic Equations
Algebra

Formulas

Quadratic Formula: x = (-b ± √(b² - 4ac)) / 2a

Theorems

Quadratic Formula

Suitable Grade Level

Grades 9-12