Chapter 8: Problem 63
Complete the square to find the \(x\) -intercepts of each function given by the equation listed. $$ f(x)=x^{2}-10 x-22 $$
Short Answer
Expert verified
The x-intercepts are at \(x = 5 + \sqrt{47}\) and \(x = 5 - \sqrt{47}\).
Step by step solution
01
- Identify coefficients
Start with the given quadratic function: \( f(x) = x^2 - 10x - 22 \) Identify the coefficients for the quadratic term, linear term, and constant term. Here, \(a = 1\), \(b = -10\), and \(c = -22\).
02
- Move the constant term
Rewrite the function by moving the constant term to the other side of the equation: \(x^2 - 10x = 22\)
03
- Complete the square
To complete the square, add and subtract \(\left( \frac{b}{2} \right)^2\) on the left side of the equation: \(x^2 - 10x + \left( \frac{-10}{2} \right)^2 = 22 + \left( \frac{-10}{2} \right)^2\)Simplify: \(x^2 - 10x + 25 = 22 + 25\) or \((x - 5)^2 = 47\)
04
- Take the square root
Take the square root of both sides of the equation to solve for x: \(x - 5 = \pm \sqrt{47}\)So, \(x = 5 \pm \sqrt{47}\)
05
- Find the x-intercepts
The x-intercepts occur where \(f(x) = 0\). Therefore, solve for \(x\) using the values found in the previous step: \(x_1 = 5 + \sqrt{47}\)\(x_2 = 5 - \sqrt{47}\)
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
quadratic functions
A quadratic function is a type of polynomial function where the highest exponent of the variable is 2. The general form of a quadratic function is given by:
f(x) = ax^2 + bx + c
Here, a, b, and c are constants. The term ax^2 is the quadratic term, bx is the linear term, and c is the constant term.
Some important properties of quadratic functions include:
f(x) = x^2 - 10x - 22
Combined, these regions help explain the shape and position of a quadratic function's graph.
f(x) = ax^2 + bx + c
Here, a, b, and c are constants. The term ax^2 is the quadratic term, bx is the linear term, and c is the constant term.
Some important properties of quadratic functions include:
- The graph of a quadratic function is a parabola.
- If a > 0, the parabola opens upwards. If a < 0, it opens downwards.
- The vertex of the parabola is the highest or lowest point on the graph.
- The parabola is symmetric about its vertex.
f(x) = x^2 - 10x - 22
Combined, these regions help explain the shape and position of a quadratic function's graph.
x-intercepts
The x-intercepts of a function are the points where the graph of the function crosses the x-axis. At these points, the output value (function value) is zero. For a given function f(x), the x-intercepts can be found by solving the equation:
f(x) = 0
In the context of our exercise, to find the x-intercepts, we set the quadratic function equal to zero and solve for x: f(x) = x^2 - 10x - 22 = 0
To solve this, we completed the square, allowing us to transform the equation into a solvable format. After completing the square and taking square roots, we arrived at the solutions:
x = 5 ± √47
Thus, the x-intercepts of the function f(x) = x^2 - 10x - 22 are given by:
x_1 = 5 + √47
x_2 = 5 - √47
These are the points where the function crosses the x-axis. Plugging these values back into the function would set f(x) to 0.
f(x) = 0
In the context of our exercise, to find the x-intercepts, we set the quadratic function equal to zero and solve for x: f(x) = x^2 - 10x - 22 = 0
To solve this, we completed the square, allowing us to transform the equation into a solvable format. After completing the square and taking square roots, we arrived at the solutions:
x = 5 ± √47
Thus, the x-intercepts of the function f(x) = x^2 - 10x - 22 are given by:
x_1 = 5 + √47
x_2 = 5 - √47
These are the points where the function crosses the x-axis. Plugging these values back into the function would set f(x) to 0.
square root
The square root is a mathematical function that, when applied to a number, produces another number which, when multiplied by itself, gives the original number. The square root of a number p is written as √p. For example, the square root of 9 is 3, because 3 × 3 = 9. Similarly:
In our exercise, we arrived at the equation:
(x - 5)^2 = 47
To solve for x, we take the square root of both sides: x - 5 = ±√47.
Adding 5 to both sides, we get:
x = 5 ± √47
Using square roots helped us solve the quadratic equation. This method is crucial for finding solutions that are not immediately obvious by simple factoring, especially when dealing with imperfect squares.
- The square root of 25 is 5.
- The square root of 1 is 1.
- The square root of 0 is 0.
- The square root of 47 remains as √47 since 47 is not a perfect square.
In our exercise, we arrived at the equation:
(x - 5)^2 = 47
To solve for x, we take the square root of both sides: x - 5 = ±√47.
Adding 5 to both sides, we get:
x = 5 ± √47
Using square roots helped us solve the quadratic equation. This method is crucial for finding solutions that are not immediately obvious by simple factoring, especially when dealing with imperfect squares.