Quadratic Formula Practice Problems - Step-by-Step Solutions

Master the quadratic formula with guided practice problems. Learn to solve ax²+bx+c=0 equations, identify coefficients, and understand discriminants through examples.

📚What You'll Master in This Practice Session
  • Identify coefficients a, b, and c in quadratic equations
  • Apply the quadratic formula X = (-b ± √(b²-4ac)) / 2a correctly
  • Calculate discriminant values to predict number of solutions
  • Solve complete quadratic equations with three parameters
  • Interpret parabola intersection points on coordinate axes
  • Check solutions by substituting back into original equations

Understanding The Quadratic Formula

Complete explanation with examples

What is a quadratic equation?

Quadratic equations (also called second degree equations) contain three numbers called parameters:

  • Parameter a a represents the position of the vertex of the parabola on the Y Y axis. A parabola can have a maximum vertex, or a minimum vertex (depending on if the parabola opens upwards or downwards).
  • Parameter b b represents the position of the vertex of the parabola on the X X axis.
  • Parameter c c represents the point of intersection of the parabola with the Y Y axis.

These three parameters are expressed in quadratic equations as follows:

aX2+bX+c=0 aX^2+bX+c=0

They are called the coefficients of the equation.

So, how do we find the value of X X ?

To find X X and be able to solve the quadratic equation, all we need to do is to input the parameters (the number values of a, b and c) from the equation into the quadratic formula, and solve for X X .

For example:

3X2+8X+4=0 3X^2+8X+4=0

Detailed explanation

Practice The Quadratic Formula

Test your knowledge with 25 quizzes

a = coefficient of x²

b = coefficient of x

c = coefficient of the independent number


\( -8x^2-5x+9=0 \)

What are the components of the equation?

Examples with solutions for The Quadratic Formula

Step-by-step solutions included
Exercise #1

a = coefficient of x²

b = coefficient of x

c = coefficient of the independent number

Identifies a,b,c

5x2+6x8=0 5x^2+6x-8=0

Step-by-Step Solution

To identify the coefficients from the quadratic equation 5x2+6x8=0 5x^2 + 6x - 8 = 0 , follow these steps:

  • Standard Form of Quadratic Equation: Compare 5x2+6x85x^2 + 6x - 8 with the standard form ax2+bx+c=0ax^2 + bx + c = 0.
  • Identify aa, bb, and cc:
    • a=5 a = 5 : The coefficient of x2x^2.
    • b=6 b = 6 : The coefficient of xx.
    • c=8 c = -8 : The constant term (independent of xx).

Therefore, from the equation 5x2+6x8=0 5x^2 + 6x - 8 = 0 , the coefficients are identified as a=5 a=5 , b=6 b=6 , and c=8 c=-8 .

Comparing with choices, we find that choice 2 is correct: a=5 a=5 , b=6 b=6 , c=8 c=-8 .

Thus, the coefficients are identified as a=5 a=5 , b=6 b=6 , c=8 c=-8 .

Answer:

a=5 a=5 b=6 b=6 c=8 c=-8

Video Solution
Exercise #2

Solve the following equation:

x2+5x+4=0 x^2+5x+4=0

Step-by-Step Solution

The parameters are expressed in the quadratic equation as follows:

aX2+bX+c=0

 

We substitute into the formula:

 

-5±√(5²-4*1*4) 
          2

 

-5±√(25-16)
         2

 

-5±√9
    2

 

-5±3
   2

 

The symbol ± means that we have to solve this part twice, once with a plus and a second time with a minus,

This is how we later get two results.

 

-5-3 = -8
-8/2 = -4

 

-5+3 = -2
-2/2 = -1

 

And thus we find out that X = -1, -4

Answer:

x1=1 x_1=-1 x2=4 x_2=-4

Video Solution
Exercise #3

a = Coefficient of x²

b = Coefficient of x

c = Coefficient of the independent number


what is the value of a a in the equation

y=3x10+5x2 y=3x-10+5x^2

Step-by-Step Solution

To solve this problem, we'll follow these steps:

  • Step 1: Rewrite the given equation in standard quadratic form if necessary.
  • Step 2: Identify the term with x2 x^2 in the equation.
  • Step 3: Extract the coefficient of x2 x^2 as a a .

Now, let's work through each step:
Step 1: The provided equation is y=3x10+5x2 y = 3x - 10 + 5x^2 . Although it's not initially in standard form, observation shows that the x2 x^2 term is clearly present.
Step 2: Locate the x2 x^2 term: in our equation, this term is 5x2 5x^2 .
Step 3: The coefficient of x2 x^2 is 5 5 . Hence, a=5 a = 5 .

Therefore, the coefficient of x2 x^2 , or a a , is a=5 a = 5 .

Answer:

a=5 a=5

Video Solution
Exercise #4

a = coefficient of x²

b = coefficient of x

c = coefficient of the independent number


what is the value of a a in the equation

y=x23x+1 y=-x^2-3x+1

Step-by-Step Solution

To determine the coefficient a a in the given quadratic equation y=x23x+1 y = -x^2 - 3x + 1 , follow these steps:

  • Step 1: Recognize the form of the quadratic equation as y=ax2+bx+c y = ax^2 + bx + c .
  • Step 2: Identify the x2 x^2 term in the equation y=x23x+1 y = -x^2 - 3x + 1 .
  • Step 3: Determine the coefficient of the x2 x^2 term, which is in front of x2 x^2 .

In the equation y=x23x+1 y = -x^2 - 3x + 1 , the term involving x2 x^2 is x2-x^2, where the coefficient a a is clearly 1-1.

Hence, the value of a a is a=1 a = -1 .

Answer:

a=1 a=-1

Video Solution
Exercise #5

a = coefficient of x²

b = coefficient of x

c = coefficient of the independent number


what is the value of b b in the equation

y=2x3x2+1 y=2x-3x^2+1

Step-by-Step Solution

To solve this problem, we need to identify the coefficients in the given quadratic equation:

  • The equation provided is y=2x3x2+1 y = 2x - 3x^2 + 1 .
  • The standard form of a quadratic equation is ax2+bx+c ax^2 + bx + c .
  • From the equation, identify:
    • The ax2 ax^2 term is 3x2 -3x^2 , indicating a=3 a = -3 .
    • The bx bx term is 2x 2x , indicating b=2 b = 2 .
    • The constant term c c is 1 1 .

Thus, the coefficient b b in the equation y=2x3x2+1 y = 2x - 3x^2 + 1 is b=2 b = 2 , which corresponds to choice 1.

Answer:

b=2 b=2

Video Solution

Frequently Asked Questions

What is the quadratic formula and when do I use it?

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The quadratic formula is X = (-b ± √(b²-4ac)) / 2a, used to solve second-degree equations in the form ax²+bx+c=0. Use it when you can't easily factor the quadratic equation or when completing the square becomes too complex.

How do I identify the coefficients a, b, and c in a quadratic equation?

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In the standard form ax²+bx+c=0: 'a' is the coefficient of X², 'b' is the coefficient of X, and 'c' is the constant term. For example, in 3X²+8X+4=0, a=3, b=8, c=4. Remember that 'a' cannot equal zero.

What does the discriminant tell me about solutions?

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The discriminant (b²-4ac) predicts the number of solutions: If positive (>0), there are two real solutions; if zero (=0), there's one solution; if negative (<0), there are no real solutions. This corresponds to how many times the parabola crosses the X-axis.

Why do quadratic equations sometimes have two solutions?

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Quadratic equations represent parabolas, which are U-shaped curves. A parabola can intersect the X-axis at two points, one point, or no points at all. Each intersection point represents a solution to the equation, which is why you can have zero, one, or two solutions.

What's the difference between quadratic equations and linear equations?

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Linear equations have variables to the first power (like 2x+3=0) and graph as straight lines, while quadratic equations have variables to the second power (like x²+2x+1=0) and graph as curved parabolas. Quadratic equations can have up to two solutions, while linear equations have exactly one solution.

How do I solve quadratic equations step by step?

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Follow these steps: 1) Write the equation in standard form ax²+bx+c=0, 2) Identify coefficients a, b, and c, 3) Substitute into the quadratic formula X = (-b ± √(b²-4ac)) / 2a, 4) Calculate the discriminant under the square root, 5) Solve for both + and - cases, 6) Check your answers by substituting back.

Can I use the quadratic formula for incomplete quadratic equations?

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Yes, but you need to identify missing terms correctly. For equations like X²+5X=0, you have a=1, b=5, c=0. For equations like X²-4=0, you have a=1, b=0, c=-4. Always ensure you're working with the complete form ax²+bx+c=0 before applying the formula.

What should I do if I get a negative number under the square root?

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A negative discriminant means the equation has no real solutions - the parabola doesn't intersect the X-axis. Double-check your calculations first, but if correct, simply state 'no real solutions' or 'no solution' as your answer. This is a valid mathematical result.

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