Core Connections Algebra 2, 2013
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Core Connections Algebra 2, 2013 View details
2. Section 3.2
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Exercise 119 Page 158

Find the vertex and the axis of symmetry of the parabola.

(-3,8) and (1,-12)

Practice makes perfect

To solve the system of equations by graphing, we will draw the graph of the quadratic function and the linear function on the same coordinate grid. Let's start with the parabola.

Graphing the Parabola

To graph the parabola, we first need to identify a, b, and c. f(x)=x^2-3x-10 ⇔ f(x)= 1x^2+( -3)x+( -10) For this equation we have that a= 1, b= -3, and c= -10. Now, we can find the vertex using its formula. Vertex of a Parabola: ( - b/2 a,f(- b/2 a) )Let's find the x-coordinate of the vertex.
- b/2a
- -3/2( 1)
- -3/2
-(-3/2)
3/2
We use the x-coordinate of the vertex to find its y-coordinate by substituting it into the given equation.
f(x)=x^2-3x-10
f( 3/2)=( 3/2)^2-3( 3/2)-10
â–Ľ
Simplify right-hand side
f(3/2)=9/4-3(3/2)-10
f(3/2)=9/4-9/2-10
f(3/2)=9/4-18/4-10
f(3/2)=9/4-18/4-40/4
f(3/2)=-49/4
The y-coordinate of the vertex is - 494. Thus, the vertex is at the point ( 32, 494). With this information, we also know that the axis of symmetry of the parabola is the line x= 32. Next, let's find two more points on the curve, one on each side of the axis of symmetry.
x x^2-3x-10 f(x)=x^2-3x-10
^2-3( )-10 -10
3 3^2-3(3)-10 -10

Both ( ,-10) and (3,-10) are on the graph. Let's form the parabola by connecting these points and the vertex with a smooth curve.

Graphing the Line

Let's now graph the linear function on the same coordinate plane. For a linear equation written in slope-intercept form, we can identify its slope m and y-intercept b. g(x)=-5x-7 ⇔ g(x)=-5x+( -7) The slope of the line is -5 and the y-intercept is -7.

Finding the Solutions

Finally, let's try to identify the coordinates of the points of intersection of the parabola and the line.

It looks like the points of intersection occur at (-3,8) and (1,-12).