All Precalculus Resources
Example Questions
Example Question #4 : Find Roots Of Quadratic Equation Using Discriminant
Use the formula b2 - 4ac to find the discriminant of the following equation: -3x2 + 6x - 3 = 0.
Then state how many roots it has, and whether they are real or imaginary. Finally, use the quadratic function to find the exact roots of the equation.
Discriminant: 0
One real root: x = -1
Discriminant: 0
One real root: x = 1
Discriminant: 72
Two distinct real roots:
Discriminant: 72
Two distinct real roots:
Discriminant: -72
Two distinct imaginary roots:
Discriminant: 0
One real root: x = 1
In the above equation, a = -3, b = 6, and c = -3. Therefore:
b2 - 4ac = (6)2 - 4(-3)(-3) = 36 - 36 = 0.
When the discriminant is greater than 0, there are two distinct real roots. When the discriminant is equal to 0, there is exactly one real root. When the discriminant is less than zero, there are no real roots, but there are exactly two distinct imaginary roots. In this case, there is exactly one real root.
Finally, we use the quadratic function to find these exact root. The quadratic formula is:
Plugging in our values of a, b, and c, we get:
This simplifies to:
which simplifies to
which gives us one answer: x = 1
This value of x is the one distinct real root of the given equation.
Example Question #3 : Find Roots Of Quadratic Equation Using Discriminant
Use the formula b2 - 4ac to find the discriminant of the following equation: x2 + 5x + 4 = 0.
Then state how many roots it has, and whether they are real or imaginary. Finally, use the quadratic function to find the exact roots of the equation.
Discriminant: 41
Two imaginary roots:
Discriminant: 0
One real root:
Discriminant: 9
Two real roots: x = -1 or x = -4
Discriminant: 9
Two real roots: x = 1 or x = 4
Discriminant: 41
Two imaginary roots:
Discriminant: 9
Two real roots: x = -1 or x = -4
In the above equation, a = 1, b = 5, and c = 4. Therefore:
b2 - 4ac = (5)2 - 4(1)(4) = 25 - 16 = 9.
When the discriminant is greater than 0, there are two distinct real roots. When the discriminant is equal to 0, there is exactly one real root. When the discriminant is less than zero, there are no real roots, but there are exactly two distinct imaginary roots. In this case, we have two real roots.
Finally, we use the quadratic function to find these exact roots. The quadratic function is:
Plugging in our values of a, b, and c, we get:
This simplifies to:
which simplifies to
which gives us two answers:
x = -1 or x = -4
These values of x are the two distinct real roots of the given equation.
Example Question #4 : Find Roots Of Quadratic Equation Using Discriminant
Use the formula b2 - 4ac to find the discriminant of the following equation: -x2 + 3x - 3 = 0.
Then state how many roots it has, and whether they are real or imaginary. Finally, use the quadratic function to find the exact roots of the equation.
Discriminant: -21
Two imaginary roots:
Discriminant: -8
Two imaginary roots: .
Discriminant: 0
One real root:
Discriminant: -8
Two imaginary roots:
Discriminant: -21
Two imaginary roots:
Discriminant: -8
Two imaginary roots: .
In the above equation, a = -1, b = 3, and c = -3. Therefore:
b2 - 4ac = (3)2 - 4(-1)(-3) = 9 - 12 = -3.
When the discriminant is greater than 0, there are two distinct real roots. When the discriminant is equal to 0, there is exactly one real root. When the discriminant is less than zero, there are no real roots, but there are exactly two distinct imaginary roots. In this case, we have two distinct imaginary roots.
Finally, we use the quadratic function to find these exact roots. The quadratic function is:
Plugging in our values of a, b, and c, we get:
This simplifies to:
Because , this simplifies to . In other words, our two distinct imaginary roots are and
Example Question #5 : Find Roots Of Quadratic Equation Using Discriminant
Use the formula b2 - 4ac to find the discriminant of the following equation: x2 + 2x + 10 = 0.
Then state how many roots it has, and whether they are real or imaginary. Finally, use the quadratic function to find the exact roots of the equation.
Discriminant: 36
Two real roots: x = 5 or x = -7
Discriminant: -36
Two imaginary roots:
Discriminant: 0
One real root: x = -1
Discriminant: -36
Two imaginary roots:
Discriminant: 36
Two real roots: x = -5 or x = 7
Discriminant: -36
Two imaginary roots:
In the above equation, a = 1, b = 2, and c = 10. Therefore:
b2 - 4ac = (2)2 - 4(1)(10) = 4 - 40 = -36.
When the discriminant is greater than 0, there are two distinct real roots. When the discriminant is equal to 0, there is exactly one real root. When the discriminant is less than zero, there are no real roots, but there are exactly two distinct imaginary roots. In this case, we have two distinct imaginary roots.
Finally, we use the quadratic function to find these exact roots. The quadratic function is:
Plugging in our values of a, b, and c, we get:
This simplifies to:
Because , this simplifies to . We can further simplify this to . In other words, our two distinct imaginary roots are and .
Example Question #6 : Find Roots Of Quadratic Equation Using Discriminant
Use the formula b2 - 4ac to find the discriminant of the following equation: x2 + 8x + 16 = 0.
Then state how many roots it has, and whether they are real or imaginary. Finally, use the quadratic function to find the exact roots of the equation.
Discriminant: 0
One real root: x = 0
Discriminant: 0
One real root: x = -4
Discriminant: 128
Two distinct real roots:
Discriminant: 0
One real root: x = 4
Discriminant: 72
Two distinct real roots:
Discriminant: 0
One real root: x = -4
In the above equation, a = 1, b = 8, and c = 16. Therefore:
b2 - 4ac = (8)2 - 4(1)(16) = 64 - 64 = 0.
When the discriminant is greater than 0, there are two distinct real roots. When the discriminant is equal to 0, there is exactly one real root. When the discriminant is less than zero, there are no real roots, but there are exactly two distinct imaginary roots. In this case, there is exactly one real root.
Finally, we use the quadratic function to find these exact root. The quadratic formula is:
Plugging in our values of a, b, and c, we get:
This simplifies to:
which simplifies to
This value of x is the one distinct real root of the given equation.
Example Question #1 : Amplitude, Period, Phase Shift Of A Trig Function
What is the amplitude of the following function?
24
14
-24
-14
24
When you think of a trigonometric function of the form y=Asin(Bx+C)+D, the amplitude is represented by A, or the coefficient in front of the sine function. While this number is -24, we always represent amplitude as a positive number, by taking the absolute value of it. Therefore, the amplitude of this function is 24.
Example Question #101 : Graphing Functions
Select the answer choice that correctly matches each function to its period.
The following matches the correct period with its corresponding trig function:
In other words, sin x, cos x, sec x, and csc x all repeat themselves every units. However, tan x and cot x repeat themselves more frequently, every units.
Example Question #2 : Amplitude, Period, Phase Shift Of A Trig Function
What is the period of this sine graph?
The graph has 3 waves between 0 and , meaning that the length of each of the waves is divided by 3, or .
Example Question #3 : Amplitude, Period, Phase Shift Of A Trig Function
Write the equation for a cosine graph with a maximum at and a minimum at .
In order to write this equation, it is helpful to sketch a graph:
The dotted line is at , where the maximum occurs and therefore where the graph starts. This means that the graph is shifted to the right .
The distance from the maximum to the minimum is half the entire wavelength. Here it is .
Since half the wavelength is , that means the full wavelength is so the frequency is just 1.
The amplitude is 3 because the graph goes symmetrically from -3 to 3.
The equation will be in the form where A is the amplitude, f is the frequency, h is the horizontal shift, and k is the vertical shift.
This equation is
.
Example Question #102 : Graphing Functions
Find the phase shift of .
3
-4
-2
2
-2
In the formula,
.
represents the phase shift.
Plugging in what we know gives us:
.
Simplified, the phase is then .
Certified Tutor
Certified Tutor