Chapter 9: Problem 19
Solve the given nonlinear system. $$ \left\\{\begin{array}{l} x y=1 \\ x+y=1 \end{array}\right. $$
Short Answer
Expert verified
The system has no real solutions.
Step by step solution
01
Express y from the Second Equation
Start by expressing one variable (e.g., \(y\)) in terms of the other variable (\(x\)) using the second equation. From \(x + y = 1\), we have \(y = 1 - x\).
02
Substitute Expression into First Equation
Substitute the expression for \(y\) into the first equation \(xy = 1\). This gives \(x(1 - x) = 1\). Simplifying yields the quadratic equation \(x - x^2 = 1\).
03
Rearrange the Quadratic Equation
Rearrange the equation \(x - x^2 = 1\) to standard quadratic form, which results in \(x^2 - x + 1 = 0\).
04
Solve the Quadratic Equation
Use the quadratic formula \(x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}\) where \(a = 1\), \(b = -1\), and \(c = 1\). Calculating the discriminant, \(b^2 - 4ac = (-1)^2 - 4 \cdot 1 \cdot 1 = 1 - 4 = -3\), which is negative. This indicates no real solutions.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Quadratic Equation
A quadratic equation is a vital part of algebra and can be identified by its standard form: \( ax^2 + bx + c = 0 \). This type of equation is called 'quadratic' because the highest power of the variable \( x \) is 2. Understanding and solving quadratic equations is crucial because they frequently appear in various mathematical contexts.
- **Key Elements**: The quadratic equation will typically involve constants \( a \), \( b \), and \( c \), where \( a \) is not equal to zero.
- **Graph Shape**: The graph of a quadratic equation is a parabola, which can open either upwards or downwards depending on the value of \( a \).
- **Solving Quadratics**: Solutions to quadratic equations can be found by factoring, completing the square, or using the quadratic formula.
Discriminant
The discriminant is a key concept linked to quadratic equations. It reveals fundamental insights about the nature of solutions. For a quadratic equation \( ax^2 + bx + c = 0 \), the discriminant is given by \( b^2 - 4ac \).
- **Importance**: The discriminant helps determine the number and type of roots (solutions) without actually solving the equation.
- **Interpretation**:
- If \( b^2 - 4ac > 0 \), there are two distinct real roots.
- If \( b^2 - 4ac = 0 \), there is one real and repeated root.
- If \( b^2 - 4ac < 0 \), there are two complex roots, implying no real solutions.
Substitution Method
The substitution method is a common technique used to solve systems of equations, including nonlinear ones. It involves replacing a variable in one equation with an expression obtained from another equation.
- **Basic Steps**:
- First, solve one of the equations for one of the variables.
- Then substitute this expression into the other equation.
- Solve the resulting equation.
- Use the solution to find the value of the other variable.
- **Benefits**: This method simplifies the system, making it easier to identify solutions by working with one variable at a time.
- **Limitations**: It might become complicated if the expressions get too complex or when dealing with many variables.