Chapter 7: Problem 11
For the following exercises, solve the system of nonlinear equations using elimination. $$ \begin{array}{l} 4 x^{2}-9 y^{2}=36 \\ 4 x^{2}+9 y^{2}=36 \end{array} $$
Short Answer
Expert verified
The solutions are \((3, 0)\) and \((-3, 0)\).
Step by step solution
01
Understanding the Problem
We have a system of two nonlinear equations:\[ 4x^2 - 9y^2 = 36 \]\[ 4x^2 + 9y^2 = 36 \]The goal is to find values of \(x\) and \(y\) that satisfy both equations simultaneously.
02
Adding the Equations
Add the two equations to eliminate \(y^2\):\[(4x^2 - 9y^2) + (4x^2 + 9y^2) = 36 + 36\]This simplifies to:\[8x^2 = 72\]
03
Solving for x
Solve \(8x^2 = 72\) for \(x^2\):\[8x^2 = 72 \x^2 = \frac{72}{8} = 9\]Take the square root of both sides:\[x = \pm 3\]
04
Subtracting the Equations
Subtract the second equation from the first to eliminate \(x^2\):\[(4x^2 - 9y^2) - (4x^2 + 9y^2) = 36 - 36\]This simplifies to:\[-18y^2 = 0\]
05
Solving for y
Solve \(-18y^2 = 0\) for \(y^2\):\[y^2 = 0\]Take the square root:\[y = 0\]
06
Verifying the Solutions
Substitute \(x = 3\) and \(x = -3\) into the original equations to verify:For \(x = 3\):1. \(4(3)^2 - 9(0)^2 = 36\)2. \(4(3)^2 + 9(0)^2 = 36\)Both equations are satisfied.For \(x = -3\):1. \(4(-3)^2 - 9(0)^2 = 36\)2. \(4(-3)^2 + 9(0)^2 = 36\)Both equations are satisfied.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Elimination Method
The elimination method is a popular technique used to solve systems of equations. This method involves combining equations to eliminate one of the variables. Once a variable is eliminated, the remaining equation, which now involves only one variable, can be solved more easily.
In the given problem:
In the given problem:
- We start with two nonlinear equations: \(4x^2 - 9y^2 = 36\) and \(4x^2 + 9y^2 = 36\).
- Adding these equations eliminates \(y^2\), leading to a simpler equation: \(8x^2 = 72\).
- Subtracting the second equation from the first eliminates \(x^2\), resulting in \(-18y^2 = 0\). This strategic approach efficiently provides isolated equations for each variable, allowing us to solve them independently.
System of Equations
A system of equations is a set of two or more equations with the same variables. Solving a system means finding a set of variable values that satisfies all equations in the system simultaneously.
There are various methods for solving systems, such as:
There are various methods for solving systems, such as:
- Graphing
- Substitution
- Elimination
- We obtained simpler quadratic equations focused on one variable at a time.
- This led to finding simple solutions for \(x\) and \(y\) which satisfy both original equations.
Quadratic Equations
Quadratic equations are polynomial equations of the second degree, generally expressed as \(ax^2 + bx + c = 0\). In the system we are solving, both equations are quadratic in terms of \(x\) and \(y\).
Here's how we approached these quadratic equations:
Here's how we approached these quadratic equations:
- After applying the elimination method, we simplified the quadratic into \(8x^2 = 72\), which can be solved by first dividing through by 8.
- The remaining equation \(x^2 = 9\) gives two potential solutions for \(x\): \(x = 3\) or \(x = -3\).
- The second quadratic \(-18y^2 = 0\) simplifies to \(y^2 = 0\), indicating a unique solution of \(y = 0\).