Core Connections Integrated II, 2015
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Core Connections Integrated II, 2015 View details
2. Section 7.2
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Exercise 109 Page 415

To complete the square,we have to add the square of half the coefficient of x to both sides of the equation.

x-intercepts: x≈ -6.70 and x≈ - 0.30
y-intercept: y=2
Vertex: (-3.5, -10.25)
Type of vertex: Minimum
Sketch:

Practice makes perfect
To complete the square, we have to add the square of half the coefficient of x to both sides of the equation.
0=x^2+7x+2
(7/2)^2=x^2+7x+2+(7/2)^2
Simplify
3.5^2=x^2+7x+2+3.5^2
3.5^2=x^2+7x+3.5^2+2
3.5^2=x^2+2(x)(3.5)+3.5^2+2
3.5^2=(x+3.5)^2+2
12.25=(x+3.5)^2+2
0=(x+3.5)^2-10.25
Now we can solve the equation for x.
0=(x+3.5)^2-10.25
Solve for x
10.25=(x+3.5)^2
(x+3.5)^2=10.25
x+3.5=± sqrt(10.25)
x=- 3.5± sqrt(10.25)
Evaluate right-hand side
lcx=- 3.5-sqrt(10.25) & (I) x=- 3.5+sqrt(10.25) & (II)

(I), (II): Subtract term

lx=-6.70156... x=-0.29843...

(I), (II): Round to 2 decimal place(s)

lx_1≈-6.70 x_2≈ -0.30
The roots are -6.70 and - 0.30. To sketch the parabola we need a few more points. Examining the function, we notice that it has a constant of 2, which means it intercepts the y-axis at y=2. Another useful point is the function's vertex. By rewriting the function in graphing form, we can find its coordinates. Graphing Form:& y=(x-a)^2+ b Vertex:& (a, b) If we rewrite the function to match this form exactly, we can identify the coordinates of its vertex. Notice that when we completed the square we were able to do one part of this procedure.
y=x^2+7x+2
y= (x+3.5)^2-10.25
y=(x-(-3.5))^2+(-10.25)
Now we can identify the coordinates of the vertex. Function:& y=(x-(-3.5))^2+( -10.25) Vertex:& (-3.5, -10.25) The vertex coordinates are (-3.5,-10.25). With this information, we can sketch the parabola.

As we can see, the vertex represents a minimum.