Core Connections Algebra 2, 2013
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Core Connections Algebra 2, 2013 View details
1. Section 7.1
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Exercise 9 Page 316

Practice makes perfect
a

The reasons why we complete the square is so that we can rewrite the function in graphing form. In this form its easier to determine the vertex.

Graphing Form:& y=a(x- h)^2+ k Vertex:& ( h, k)To complete the square we have to add the square of half the coefficient to x.

y=x^2+5x+7
y+(5/2)^2=x^2+5x+7+(5/2)^2
â–¼
Simplify
y+(5/2)^2=x^2+5x+(5/2)^2+7
y+(5/2)^2=x^2+2x(5/2)+(5/2)^2+7
y+(5/2)^2=(x+5/2)^2+7
y+25/4=(x+5/2)^2+7
y=(x+5/2)^2+7-25/4
y=(x+5/2)^2+28/4-25/4
y=(x+5/2)^2+3/4

a=- (- a)

y=(x-(- 5/2))^2+3/4

Having written the function in graphing form, we can identify the vertex. Graphing Form:& y=(x-( - 5/2))^2+ 3/4 Vertex:& ( - 5/2, 3/4)

b

In any function the y-intercept is given by its constant. If we examine the function, we can identify the function's constant as 7.

y=x^2+5x+ 7 We could also determine this by substituting x=0 into the function and simplifying.
c

Examining the function, we see that the x^2-term's coefficient is positive. This means that the parabola must open upwards. Let's plot the vertex and y-intercept from Parts A and B. Let's also include the parabola's line of symmetry, which is a vertical line through the parabola's vertex.

The parabola's symmetry allows us to identify a third point through which the line passes that is on y=7. This point will be equidistant with the y-intercept from the line of symmetry.

The third point is at (- 5,7). Now we can draw an accurate parabola.