McGraw Hill Glencoe Algebra 2, 2012
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McGraw Hill Glencoe Algebra 2, 2012 View details
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Exercise 1 Page 383

Start by identifying the values of a, b, and c.

Between 0 and 1, and between 3 and 4.

Practice makes perfect
The related graph of the given quadratic equation is the graph of the quadratic function on the left-hand side of the equation. Equation:& x^2-4x+1=0 Related Function:& y=x^2-4x+1 To draw the graph of the quadratic function, written in standard form, we must start by identifying the values of a, b, and c. y=x^2-4x+1 ⇔ y=1x^2+(- 4)x+1

We can see that a=1, b=- 4, and c=1. Now, we will follow four steps to graph the function.

  1. Find the axis of symmetry.
  2. Calculate the vertex.
  3. Identify the y-intercept and its reflection across the axis of symmetry.
  4. Connect the points with a parabola.

Finding the Axis of Symmetry

The axis of symmetry is a vertical line with equation x=- b2a. Since we already know the values of a and b, we can substitute them into the formula.
x=- b/2a
x=- - 4/2(1)
Simplify right-hand side
x=-- 4/2
x=-(- 2)
x=2
The axis of symmetry of the parabola is the vertical line with equation x=2.

Calculating the Vertex

To calculate the vertex, we need to think of y as a function of x, y=f(x). We can write the expression for the vertex by stating the x- and y-coordinates in terms of a and b. Vertex: ( - b/2a, f( - b/2a ) ) Note that the formula for the x-coordinate is the same as the formula for the axis of symmetry, which is x=2. Thus, the x-coordinate of the vertex is also 2. To find the y-coordinate, we need to substitute 2 for x in the function's rule.
y=x^2-4x+1
y= 2^2-4( 2)+1
Simplify right-hand side
y=4-4(2)+1
y=4-8+1
y=- 3
We found the y-coordinate, and now we know that the vertex is (2,- 3).

Identifying the y-intercept and its Reflection

The y-intercept of the graph of a quadratic function written in standard form is given by the value of c. Thus, the point where our graph intercepts the y-axis is (0,1). Let's plot this point and its reflection across the axis of symmetry.

Connecting the Points

We can now draw the graph of the function. Since a=1, which is positive, the parabola will open upwards. Let's connect the three points with a smooth curve.

The roots are the x-coordinates where graph crosses the x-axis. By looking at the graph, we can state that the roots are located between 0 and 1, and between 3 and 4.