Mathematics, 21.07.2020 20:01 shawn20034

PLEASE HELP 1. Find the area of the region enclosed by the graph of .

2. The line is an axis of symmetry of the graph of Find $$\frac{b}{a}$.$ .

3. The graph of is shown below. Find $a \cdot b \cdot c$ . (The distance between the grid lines is one unit, picture of graph attached.)

4. Geometrically speaking, a parabola is defined as the set of points that are the same distance from a given point and a given line. The point is called the focus of the parabola and the line is called the directrix of the parabola. Suppose $\mathcal{P}$ is a parabola with focus and directrix . The point is on $\mathcal{P}$ because is 5 units away from both the focus and the directrix. If we write the equation whose graph is $\mathcal{P}$ in the form , then what is ?

5. (This is a Writing Problem - please please please explain and answer the question thoroughly!) A quadratic of the form has roots of $x = 3 + \sqrt{5}$ and $x = 3 - \sqrt{5}.$ The graph of is a parabola. Find the vertex of this parabola.

If you do manage to answer every single one of these correctly, THANK YOU SO MUCH and please know you are very much appreciated! :)

PLEASE HELP

1. Find the area of the regio

Answers: 2

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Answers

Answer from: punkieladie

1. $Area=16\,\pi=50.265$

2.- $\frac{b}{a} =-8$

3. $y=\frac{1}{2} x^2+3x+\frac{5}{2}$

4. $a+b+c=\frac{17}{4}$

5. the vertex is located at: (3, 10)

Step-by-step explanation:

1. If we rewrite the formula of the conic given by completing squares, we can find what conic we are dealing with:

$(x^2-2x)+(y^2+6y)=6\\\,\,\,\,\,\,+1\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,+9\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,+10\\(x-1)^2+(y+3)^2=16\\(x-1)^2+(y+3)^2=4^2$

which corresponds to a circle of radius 4, and we know what the formula is for a circle of radius R, then:

$Area=\pi\,R^2=\pi\,4^2=16\,\pi=50.265$

If x=4 is the axis of symmetry of the parabola

y=ax^2+bx+c

then recall the formula to obtain the position of the x-value of the vertex:

$x_{vertex}=-\frac{b}{2a} \\4=-\frac{b}{2a}\\4\,(-2)=\frac{b}{a} \\\frac{b}{a} =-8$

From the graph attached, we see that the vertex of the parabola is at the point: (-3, -2) on the plane, so we can write the general formula for a parabola in vertex form:

$y-y_{vertex}=a\,(x-x_{vertex})^2\\y-(-2)=a\,(x-(-3))^2\\y+2=a(x+3)^2$

and now find the value of the parameter "a" by requesting the parabola to go through another obvious point, let's say the zero given by (-1, 0) at the crossing of the x-axis:

$y+2=a\,(x+3)^2\\0+2=a(-1+3)^2\\2=a\,2^2\\a=\frac{1}{2}$

So the equation of the parabola becomes:

$y+2=\frac{1}{2} (x+3)^2\\y+2=\frac{1}{2} (x^2+6x+9)\\y+2=\frac{1}{2} x^2+3x+\frac{9}{2} \\y=\frac{1}{2} x^2+3x+\frac{9}{2} -2\\y=\frac{1}{2} x^2+3x+\frac{5}{2}$

From the location of the focus of the parabola as (4, 3) and the directrix as y=1, we conclude that we have a parabola with dominant vertical axis of symmetry, displaced from the origin of coordinates, and responding to the following type of formula:

$(x-h)^2=4\,p\,(y-k)$

with focus at: (h,k+p)

directrix given by the horizontal line y=k-p

and symmetry axis given by the vertical line x=h

Since we are given that the focus is at (4, 3), we know that h=4 , and that k+p=3

Now given that the directrix is: y = 1, then:

$y=k-p\\1=k-p$

Now combining both equations with these unknowns:

$k+p=3\\k=3-p$

$1=k-p\\k=1+p$

then :

$1+p=3-p\\2p=3-1\\2p=2\\p=1$

and we now can solve for k:

k=1+p=1+1=2

Then we have the three parameters needed to write the equation for this parabola:

$(x-h)^2=4\,p\,(y-k)\\(x-4)^2=4\,(1)\,(y-2)\\x^2-8x+16=4y-8\\4y=x^2-8x+16+8\\4y=x^2-8x+24\\y=\frac{1}{4} x^2-2x+6$

therefore: $a=\frac{1}{4} , \,\,\,b=-2,\,\,and\,\,\,c=6$

Then $a+b+c=\frac{17}{4}$

The vertex of a parabola can easily found because they give you the roots of the quadratic function, which are located equidistant from the symmetry axis. So we know that is one root is at $x=3+\sqrt{5}$ and the other root is at $x=3-\sqrt{5}$

then the x position of the vertex must be located at x = 3 (equidistant from and in the middle of both solutions. Then we can use the formula for the x of the vertex to find b:

$x_{vertex}=-\frac{b}{2a}\\3=-\frac{b}{2\,(-2)}\\ b=12$