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

Solve the following equation:

\( -2x^2+22x-60=0 \)

Examples with solutions for The Quadratic Formula

Step-by-step solutions included
Exercise #1

Solve the following equation:

2x210x12=0 2x^2-10x-12=0

Step-by-Step Solution

Let's recall the quadratic formula:

Quadratic formula | The formula

We'll substitute the given data into the formula:

x=(10)±10242(12)22 x={{-(-10)\pm\sqrt{-10^2-4\cdot2\cdot(-12)}\over 2\cdot2}}

Let's simplify and solve the part under the square root:

x=10±100+964 x={{10\pm\sqrt{100+96}\over 4}}

x=10±1964 x={{10\pm\sqrt{196}\over 4}}

x=10±144 x={{10\pm14\over 4}}

Now we'll solve using both methods, once with the addition sign and once with the subtraction sign:

x=10+144=244=6 x={{10+14\over 4}} = {24\over4}=6

x=10144=44=1 x={{10-14\over 4}} = {-4\over4}=-1

We've arrived at the solution: X=6,-1

Answer:

x1=6 x_1=6 x2=1 x_2=-1

Video Solution
Exercise #2

a = coefficient of x²

b = coefficient of x

c = coefficient of the independent number


x2+7x=0 x^2+7x=0

What are the components of the equation?

Step-by-Step Solution

Let's solve the problem step-by-step:

First, consider the given equation:

x2+7x=0 x^2 + 7x = 0

This equation is almost in the standard form of a quadratic equation:

ax2+bx+c=0 ax^2 + bx + c = 0

Where:

  • a a is the coefficient of x2 x^2
  • b b is the coefficient of x x
  • c c is the constant term (independent number)

Let's identify each of these components from the given equation:

  • For a a : The term with x2 x^2 is x2 x^2 . In this case, the coefficient is implicitly 1, so a=1 a = 1 .
  • For b b : The term with x x is 7x 7x . The coefficient of x x is 7, so b=7 b = 7 .
  • For c c : There is no independent constant term visible, so we assume c=0 c = 0 .

Thus, the components of the quadratic equation are:

a=1 a = 1 , b=7 b = 7 , c=0 c = 0

The correct choice from the provided options is : a=1 a=1 , b=7 b=7 , c=0 c=0

Answer:

a=1 a=1 b=7 b=7 c=0 c=0

Video Solution
Exercise #3

a = coefficient of x²

b = coefficient of x

c = coefficient of the independent number


56x2+12x=0 5-6x^2+12x=0

What are the components of the equation?

Step-by-Step Solution

Let's solve this problem step-by-step by identifying the coefficients of the quadratic equation:

First, examine the given equation:

56x2+12x=05 - 6x^2 + 12x = 0

To make it easier to identify the coefficients, we rewrite the equation in the standard quadratic form:

6x2+12x+5=0-6x^2 + 12x + 5 = 0

In this expression, we can now directly identify the coefficients:

  • The coefficient of x2 x^2 (quadratic term) is a=6 a = -6 .
  • The coefficient of x x (linear term) is b=12 b = 12 .
  • The constant term (independent number) is c=5 c = 5 .

Thus, the components of the quadratic equation are:

a=6 a = -6 , b=12 b = 12 , c=5 c = 5

By comparing these values to the multiple-choice options, we can determine that the correct choice is:

Choice 4: a=6 a = -6 , b=12 b = 12 , c=5 c = 5

Therefore, the final solution is:

a=6 a = -6 , b=12 b = 12 , c=5 c = 5 .

Answer:

a=6 a=-6 b=12 b=12 c=5 c=5

Video Solution
Exercise #4

a = coefficient of x²

b = coefficient of x

c = coefficient of the constant term


What is the value of c c in the function y=x2+25x y=-x^2+25x ?

Step-by-Step Solution

Let's recall the general form of the quadratic function:

y=ax2+bx+c y=ax^2+bx+c The function given in the problem is:

y=x2+25x y=-x^2+25x c c is the free term (meaning the coefficient of the term with power 0),

In the function in the problem there is no free term,

Therefore, we can identify that:

c=0 c=0 Therefore, the correct answer is answer A.

Answer:

c=0 c=0

Video Solution
Exercise #5

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

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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