Umm, I don't feel like typing (too lazy and tired to do that lol) so I will attach a written file.
BTW-
Radius is HALF the Diameter.
Diameter is that straight line that goes across the center of the circle.
Radius is basically a line from the center of the circle to any of the side of the circle.
Circumference is basically the perimeter of the circle, or the border or it. It is the Diameter times pi (it said to use 3.14 for pi). It can also be 2 times the Radius times pi (3.14) (since Radius is half the Diameter).
Area is the region inside the circle. Area is the Radius squared (to the power of 2, whatever) times pi (simplified as 3.14).
Okie, now the answers.
^^^Too lazy to put the unit lol.
The boundary of the lawn in front of a building is represented by the parabola
y = (x^2) /16 + x - 2
And you have three questions which require to find the focus, the vertex and the directrix of the parabola.
Note that it is a regular parabola (its symmetry axis is paralell to the y-axis).
1) Focus:
It is a point on the symmetry axis => x = the x-component of the vertex) at a distance equal to the distance between the directrix and the vertex).
In a regular parabola, the y - coordinate of the focus is p units from the y-coordinate of the focus, and p is equal to 1/(4a), where a is the coefficient that appears in this form of the parabola's equation: y = a(x - h)^2 + k (this is called the vertex form)
Then we will rearrange the standard form, (x^2)/16 + x - 2 fo find the vertex form y = a(x-h)^2 + k
What we need is to complete a square. You can follow these steps.
1) Extract common factor 1/16 => (1/16) [ (x^2) + 16x - 32]
2) Add (and subtract) the square of the half value of the coefficent ot the term on x =>
16/2 = 8 => add and subtract 8^2 => (1/16) [ (x^2) + 16 x + 8^2 - 32 - 8^2]
3) The three first terms inside the square brackets are a perfect square trinomial: =>
(1/16) [ (x+8)^2 - 32 - 64] = (1/16) [ (x+8)^2 - 96] =>
(1/16) [(x+8)^2 ] - 96/16 =>
(1/16) (x +8)^2 - 6
Which is now in the form a(x - h)^2 + k, where:
a = 1/16 , h = - 8, and k = -6
(h,k) is the vertex: h is the x-coordinate of the vertex, and k is the y-coordinate of the vertex.
=> a = 1/16 => p =1/4a = 16/4 = 4
y-componente of the focus = -6 + 4 = -2
x-component of the focus = h = - 8
=> focus = (-8, -2)
2) Vertex
We found it above, vertex = (h,k) = (-8,-6)
3) Directrix
It is the line y = p units below the vertex = > y = -6 - 4 = -10
y = -10
Divide the irregular figure into rectangles
Area of rectangle = l * w
4 * 5 = 20 in^2
5 * 12 = 60 in^2
7 * 11 = 77 in^2
Add them together
20 + 60 + 77 = 157 in^2
(Sorry if the picture isn’t neat)
