Problem 58 - BIG IDEAS MATH Algebra 2: Common Core Student Edition 2015

Question

Solve the system by graphing. \(y=x^2+6\) \(y=3 x+4\)

Step-by-Step Solution

Answer

Points of intersection estimated from the graph which are the solutions to the system of equations cannot be exact due to the issue of scale or due to rounding errors. One should check the validity of the solution by substituting back into the original equations.

Step 1: Graph the Equations

Plot both equations on the same graph. The quadratic equation \(y = x^2+6\) can be graphed by plotting points. The points might include (-2,10), (0,6), and (2,10). The linear equation \(y=3x+4\) can be graphed by drawing a line with slope 3 and y-intercept 4. It crosses the y-axis at (0,4) and the x-axis at the point \(-\frac{4}{3},0\).

Step 2: Locate the Intersection Points

After graphing both equations on the same set of axes, find the points where the parabola and the line intersect. These points denote the solutions to the system of equations.

Step 3: Identify the Solutions

Intersections might not be exact due to rounding inaccuracies, however you can estimate these points and check it by inserting these values into the original equations to confirm the validity of the solutions.

Key Concepts

Quadratic Equations

Quadratic equations are characterized by the presence of an equation in the form of a parabola. The standard form of a quadratic equation is \(y = ax^2 + bx + c\). The distinctive feature is the \(x^2\) term, which makes the equation non-linear. In simple terms, a quadratic equation creates a U-shaped curve on graphs, known as a parabola. The parabola either opens upward or downward depending on the coefficient of the \(x^2\) term. If it's positive, the parabola opens upwards like a smile, and if negative, it opens downwards like a frown.

When graphing a quadratic equation such as \(y = x^2 + 6\), it involves tracking its vertex and direction. The vertex represents the highest or lowest point on the graph. With the equation \(y = x^2 + 6\), the vertex is (0,6), meaning the lowest point is at y=6. The parabola symmetrically stretches on either side from this vertex point. By plotting additional points and connecting them smoothly, you create the full shape of the parabola. This curve indicates all the possible values of \(y\) for different \(x\).

Understanding these pieces is crucial when tackling quadratic equations, especially within systems that involve different types of equations.

Linear Equations

Linear equations are much simpler compared to quadratic ones. They are called 'linear' because their graph is a straight line. The general form for a linear equation is \(y = mx + b\), where \(m\) is the slope, and \(b\) is the y-intercept. The slope defines the angle of the line, and the y-intercept is where the line crosses the y-axis. For example, in the equation \(y = 3x + 4\), \(m=3\) denotes a steep slope, and \(b=4\) indicates the line crosses the y-axis at (0,4).

When graphing a linear equation, you only need two points to graph a line precisely:

• The y-intercept: This is always one point you can start with.
• Use the slope to find another point: From the y-intercept, use the slope to locate another point on the graph. If the slope is 3, move up three units and one unit right to find a second point.

Using a ruler or a straight edge, draw a line through these two points, extending it in both directions. This line represents all possible solutions to the equation. Despite its simplicity, linear equations play a foundational role in more complex systems, often intersecting with more complex graphs like parabolas.

Graphing

Graphing is a visualization method used to solve systems of equations, such as a combination of quadratic and linear equations. By plotting graphs simultaneously, one can find solution points through their intersections.

To solve systems of equations graphically, follow these steps:

• Graph each equation on the same set of axes: Input your equations, such as \(y = x^2 + 6\) and \(y = 3x + 4\), separately and find points to plot on the graph.
• Draw each graph: For quadratics, connect the points to form a smooth curve. For linears, use the slope formula to draw a straight line.
• Locate intersection points: Look at the graph to find where the line and curve meet. These intersection points are the solutions to your system.

Graphing offers a useful way to visualize relationships between equations, observing where their solutions overlap. It also provides an intuitive sense of how different variables affect each other within a given system. While the graphical method might sometimes lead to estimated solutions due to the limitations of hand-drawn graphs, it's an essential skill, especially as it integrates both visual analysis and algebraic calculations.