Chapter 9: Problem 23
Solve each quadratic equation using the square root property. Express imaginary solutions in \(a+b i\) form. $$(y+3)^{2}=-18$$
Short Answer
Expert verified
The solutions to the quadratic equation \((y+3)^2=-18\) are \(y = -3 + 3i\) and \(y = -3 - 3i\).
Step by step solution
01
Rewrite the equation in terms of y
We can rewrite the equation as \((y+3)^2 = -1 * (3 * 3)^2)\) to make it clear that we're looking at the square of -3, or -9, on the right side of the equation.
02
Apply the square root property
Applying the square root property gives us two equations. The first is \(y + 3 = sqrt(-9)\), and the second is \(y + 3 = -sqrt(-9)\). Simplifying these gives us \(y + 3 = sqrt(-1) * sqrt(9)\), resulting in \(y + 3 = ± 3i\).
03
Simplify to find the value of y
Subtracting 3 from both sides in the final equation gives us the solutions for \(y\). Our two solutions are \(y = -3 + 3i\) and \(y = -3 - 3i\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Square Root Property
The square root property is a key tool in solving quadratic equations, especially when these equations take the form \((x+c)^2 = n\). This property tells us that if we have an equation like this, we can solve it as \(x+c = \sqrt{n}\) or \(x+c = -\sqrt{n}\). In other words, after isolating the square on one side, we take both the positive and negative square roots of the other side.
Here is a step-by-step guide on how to use the square root property:
Here is a step-by-step guide on how to use the square root property:
- Isolate the square: Ensure that the squared term is by itself on one side of the equation, just like in our example, \((y+3)^2 = -18\).
- Apply the square root: Take the square root of both sides of the equation, remembering to consider both the positive and negative values. So here we'll get \(y + 3 = \sqrt{-18}\) or \(y + 3 = -\sqrt{-18}\).
- Simplify the expression: In our case, \(\sqrt{-18}\) becomes \(\pm3i\). Remember that the square root of a negative number brings us into the world of imaginary numbers.
- Solve for the variable: Finish by isolating \(y\) (in our example), to find your solutions.
Imaginary Numbers
When solving equations, sometimes the square root of a negative number appears, defining the realm of imaginary numbers. The unit imaginary number is \(i\), defined as \(i = \sqrt{-1}\). This means that \(i^2 = -1\).
Imaginary numbers allow the representation of roots of negative numbers in a systematic way. When we solve the quadratic equation \((y+3)^2 = -18\), we encounter \(\sqrt{-9}\). Here's what happens:
Imaginary numbers allow the representation of roots of negative numbers in a systematic way. When we solve the quadratic equation \((y+3)^2 = -18\), we encounter \(\sqrt{-9}\). Here's what happens:
- Recognize the negative inside the square root: Identify the negative sign and separate it using \(\sqrt{-1}\), which is \(i\).
- Simplify the real part: The real part of \(\sqrt{9}\) is \(3\). Thus, \(\sqrt{-9}\) becomes \(3i\).
Complex Numbers
Complex numbers expand the usefulness of numbers beyond traditional real numbers by including both a real and an imaginary component. They generally take the form \(a + bi\), where \(a\) is the real part, and \(bi\) is the imaginary part. In the context of our quadratic equation, solutions like \(y = -3 + 3i\) are noted.
Here's a breakdown of these components:
Here's a breakdown of these components:
- Real Component: In \(-3 + 3i\), \(-3\) is the real part. This value exists on a traditional number line.
- Imaginary Component: \(3i\) represents the imaginary part. The imaginary number axis is perpendicular to the real number line.