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Use the elimination method to find all solutions of the system of equations. $$\left\\{\begin{array}{l}x^{2}-2 y=1 \\\x^{2}+5 y=29\end{array}\right.$$

Short Answer

Expert verified
Solutions: (x,y) = (3,4) and (-3,4)

Step by step solution

01

Set Up the Equations for Elimination

We have the system of equations: \( x^2 - 2y = 1 \) and \( x^2 + 5y = 29 \). To use elimination, we will subtract the first equation from the second.
02

Eliminate Variable 'x²'

Subtract the first equation from the second:\( (x^2 + 5y) - (x^2 - 2y) = 29 - 1 \).This simplifies to \( 7y = 28 \).
03

Solve for 'y'

Divide each side of the equation \( 7y = 28 \) by 7:\( y = 4 \).
04

Substitute 'y' into One of the Original Equations

Take the value \( y = 4 \) and substitute it back into the first equation:\( x^2 - 2(4) = 1 \).
05

Solve for 'x²'

Simplify the equation:\( x^2 - 8 = 1 \).Adding 8 to both sides gives \( x^2 = 9 \).
06

Solve for 'x'

To find \( x \), take the square root of both sides of \( x^2 = 9 \):\( x = 3 \) or \( x = -3 \).
07

Verify Solution in Second Equation

Substitute \( y = 4 \), \( x = 3 \), and \( x = -3 \) into the second equation:- For \( x = 3 \): \( 3^2 + 5(4) = 9 + 20 = 29 \), which is correct.- For \( x = -3 \): \((-3)^2 + 5(4) = 9 + 20 = 29 \), also correct.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

System of Equations
A system of equations involves finding values for the variables that satisfy all given equations simultaneously. In our case, we have two equations: \(x^2 - 2y = 1\) and \(x^2 + 5y = 29\). These equations contain two variables, \(x\) and \(y\), quadratic in nature. We aim to find specific pairs of \((x, y)\) that solve both equations at the same time.
To tackle this, we can employ the elimination method. This method involves aligning the equations in such a way that one variable can be eliminated by addition or subtraction, making the system less complex to solve. Here, we realized both equations have \(x^2\) terms that can be canceled out when subtracted from one another. By doing this, we simplify our system to focus solely on solving for \(y\). Once we know \(y\), we can plug it back into one of the original equations to find the corresponding \(x\) values.
Solve for Variables
Solving for variables in a system of equations usually involves a step-by-step process. In our problem, the elimination method is the first move to determine \(y\). By subtracting one equation from the other, achieving \(7y = 28\) allows us to quickly solve for \(y\) by dividing both sides by 7, giving \(y = 4\).
With \(y\) known, the next step is to plug this value back into either of the original equations to solve for \(x\). Substituting \(y = 4\) into \(x^2 - 2y = 1\) simplifies the equation to \(x^2 - 8 = 1\). Adjusting the constants gives \(x^2 = 9\). Taking the square root, we find \(x = 3\) or \(x = -3\).
This systematic approach ensures each variable is accurately determined, resulting in a comprehensive solution that satisfies both equations.
Quadratic Equations
Quadratic equations play a major role in systems like ours, where variables are raised to the power of 2. A standard quadratic equation has the form \(ax^2 + bx + c = 0\) and can yield two solutions based on the properties of square roots.
After solving for \(y\), we encountered \(x^2 = 9\). In this specific quadratic scenario, solving for \(x\) requires taking the square root of both sides, leading to \(x = 3\) or \(x = -3\). These twin solutions emerge due to the inherent nature of quadratic equations where both positive and negative roots are valid.
Verifying these solutions within the context of the second equation in our system is essential. It ensures that both solutions are correct and consistent with all given conditions, confirming the integrity of the solution process. Remember, quadratic equations will often result in multiple solutions, a key aspect of why they can initially seem complex but produce rich results when solved methodically.

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Most popular questions from this chapter

Use a calculator that can perform matrix operations to solve the system, as in Example 7. $$\left\\{\begin{array}{lr} x+\frac{1}{2} y-\frac{1}{3} z= & 4 \\ x-\frac{1}{4} y+\frac{1}{6} z= & 7 \\ x+y-z= & -6 \end{array}\right.$$

Find the inverse of the matrix. For what value(s) of \(x\) if any, does the matrix have no inverse? $$\left[\begin{array}{cc} x & 1 \\ -x & \frac{1}{x-1} \end{array}\right]$$

\(A\) square root of a matrix \(B\) is a matrix \(A\) with the property that \(A^{2}=B\). (This is the same definition as for a square root of a number.) Find as many square roots as you can of each matrix: $$\left[\begin{array}{ll} 4 & 0 \\ 0 & 9 \end{array}\right] \quad\left[\begin{array}{ll} 1 & 5 \\ 0 & 9 \end{array}\right]$$ [Hint: If \(A=$$\left[\begin{array}{ll}a & b \\ c & d\end{array}\right]\) write the equations that \(a, b, c,\) and \(d\) would have to satisfy if \(A\) is the square root of the given matrix.]

Nutrition A nutritionist is studying the effects of the nutrients folic acid, choline, and inositol. He has three types of food available, and each type contains the following amounts of these nutrients per ounce: \begin{array}{|l|ccc|} \hline & \text { Type A } & \text { Type B } & \text { Type C } \\ \hline \text { Folic acid (mg) } & 3 & 1 & 3 \\ \text { Choline (mg) } & 4 & 2 & 4 \\ \text { Inositol (mg) } & 3 & 2 & 4 \\ \hline \end{array} (a) Find the inverse of the matrix $$\left[\begin{array}{lll} 3 & 1 & 3 \\ 4 & 2 & 4 \\ 3 & 2 & 4 \end{array}\right]$$ and use it to solve the remaining parts of this problem. (b) How many ounces of each food should the nutritionist feed his laboratory rats if he wants their daily diet to contain \(10 \mathrm{mg}\) of folic acid, \(14 \mathrm{mg}\) of choline, and \(13 \mathrm{mg}\) of inositol? (c) How much of each food is needed to supply \(9 \mathrm{mg}\) of folic acid, 12 mg of choline, and 10 mg of inositol? (d) Will any combination of these foods supply \(2 \mathrm{mg}\) of folic acid, \(4 \mathrm{mg}\) of choline, and \(11 \mathrm{mg}\) of inositol?

Evaluate the determinant, using row or column operations whenever possible to simplify your work. $$\left|\begin{array}{rrrr} 2 & -1 & 6 & 4 \\ 7 & 2 & -2 & 5 \\ 4 & -2 & 10 & 8 \\ 6 & 1 & 1 & 4 \end{array}\right|$$

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