Solve the Quadratic Equation: (1/2)x² - 3x + 2.5 = 0

Quadratic Formula with Fractional Coefficients

Solve the following equation:

12x23x+212=0 \frac{1}{2}x^2-3x+2\frac{1}{2}=0

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Find X
00:06 Multiply to eliminate fractions
00:14 Identify the coefficients
00:26 Use the roots formula
00:45 Substitute appropriate values according to the given data and solve
01:09 Calculate the square and products
01:21 Calculate the square root of 16
01:31 These are the 2 possible solutions (addition,subtraction)
01:54 And this is the solution to the question

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Solve the following equation:

12x23x+212=0 \frac{1}{2}x^2-3x+2\frac{1}{2}=0

2

Step-by-step solution

To solve the quadratic equation 12x23x+212=0 \frac{1}{2}x^2 - 3x + 2\frac{1}{2} = 0 , we will follow these steps:

  • Step 1: Convert the mixed number to an improper fraction or decimal for uniformity in calculations.
  • Step 2: Identify the coefficients a a , b b , and c c .
  • Step 3: Apply the quadratic formula to find the roots x1 x_1 and x2 x_2 .

Step 1: Rewriting the equation with decimals, we have:

12x23x+2.5=0 \frac{1}{2}x^2 - 3x + 2.5 = 0

Step 2: The equation is already in standard form, where a=12 a = \frac{1}{2} , b=3 b = -3 , and c=2.5 c = 2.5 .

Step 3: Apply the quadratic formula:

x=b±b24ac2a x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}

Calculate the discriminant (Δ \Delta ):

Δ=b24ac=(3)24122.5=95=4 \Delta = b^2 - 4ac = (-3)^2 - 4 \cdot \frac{1}{2} \cdot 2.5 = 9 - 5 = 4

Since the discriminant is positive, there are two real solutions.

Calculate the roots:

x=(3)±4212 x = \frac{-(-3) \pm \sqrt{4}}{2 \cdot \frac{1}{2}}

x=3±21 x = \frac{3 \pm 2}{1}

Thus, the solutions are:

  • x1=3+21=5 x_1 = \frac{3 + 2}{1} = 5
  • x2=321=1 x_2 = \frac{3 - 2}{1} = 1

Therefore, the solutions to the equation are x1=5 x_1 = 5 and x2=1 x_2 = 1 .

From the provided choices, the correct answer is:

x1=5,x2=1 x_1=5,x_2=1

3

Final Answer

x1=5,x2=1 x_1=5,x_2=1

Key Points to Remember

Essential concepts to master this topic
  • Formula: Use x=b±b24ac2a x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} for any quadratic equation
  • Discriminant: Calculate Δ=(3)24(12)(2.5)=95=4 \Delta = (-3)^2 - 4(\frac{1}{2})(2.5) = 9 - 5 = 4
  • Verification: Substitute x=5 x = 5 : 12(25)3(5)+2.5=0 \frac{1}{2}(25) - 3(5) + 2.5 = 0

Common Mistakes

Avoid these frequent errors
  • Forgetting to multiply by 2a in the denominator
    Don't calculate just x=3±212 x = \frac{3 \pm 2}{\frac{1}{2}} = wrong fractions! This ignores the "2" in the formula's denominator. Always use 2a=212=1 2a = 2 \cdot \frac{1}{2} = 1 as your complete denominator.

Practice Quiz

Test your knowledge with interactive questions

a = Coefficient of x²

b = Coefficient of x

c = Coefficient of the independent number


what is the value of \( a \) in the equation

\( y=3x-10+5x^2 \)

FAQ

Everything you need to know about this question

Why do I get a positive discriminant here?

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A positive discriminant means you have two real solutions! When Δ=4>0 \Delta = 4 > 0 , your parabola crosses the x-axis at two points: x = 1 and x = 5.

Can I solve this by factoring instead?

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Yes! You can multiply by 2 to get x26x+5=0 x^2 - 6x + 5 = 0 , which factors as (x1)(x5)=0 (x-1)(x-5) = 0 . Both methods give the same answers!

What if my coefficients are more complex fractions?

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The quadratic formula works with any coefficients! Just be extra careful with arithmetic. Consider converting mixed numbers to decimals like 212=2.5 2\frac{1}{2} = 2.5 to avoid calculation errors.

How do I check my work with fractional coefficients?

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Substitute each solution back into the original equation. For x = 5: 12(25)3(5)+2.5=12.515+2.5=0 \frac{1}{2}(25) - 3(5) + 2.5 = 12.5 - 15 + 2.5 = 0

Why is the denominator just 1 in the final step?

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Because 2a=212=1 2a = 2 \cdot \frac{1}{2} = 1 ! When you have a=12 a = \frac{1}{2} , multiplying by 2 gives you a denominator of 1, which simplifies your calculations.

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