1) The graph of (x-3)^2 + (y-5)^2=16 is reflected over the line y=2. The new graph is the graph of the equation x^2 + Bx + y^2 + Dy + F = 0 for some constants B, D, and F. Find B+D+F.
2) 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 P is a parabola with focus (4,3) and directrix y=1. The point (8,6) is on P because (8,6) is 5 units away from both the focus and the directrix.
If we write the equation whose graph is P in the form ax^2+bx+c, then what is a+b+c?
1) The graph of (x-3)^2 + (y-5)^2=16 is reflected over the line y=2. The new graph is the graph of the equation x^2 + Bx + y^2 + Dy + F = 0 for some constants B, D, and F. Find B+D+F.
The original graph is a circle with a center at (3, 5) and a radius of 4 units.
If it is reflected across the line y = 2, the center of the new circle is (3, -1) and the equation is given by
(x - 3)^2 + ( y + 1)^2 = 16 expanding this we have
x^2 - 6x + 9 + y^2 + 2y + 1 = 16 simplify
x^2 - 6x + y^2 + 2y + 10 = 16
x^2 - 6x + y^2 + 2y - 6 = 0 and B = -6 and D = 2 and F = -6 so........B + D + F = -6 + 2 - 6 = -10
Here's a graph of the situation : https://www.desmos.com/calculator/qjdm7ag3vb
2) 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 P is a parabola with focus (4,3) and directrix y=1. The point (8,6) is on P because (8,6) is 5 units away from both the focus and the directrix.
If we write the equation whose graph is P in the form ax^2+bx+c, then what is a+b+c?
The vertex of this parabola will lie at (4,2)
And we have this form
y = a(x - h)^2 + k and (h,k) = the vertex = (4,2) and since (8,6) is on the graph, we can solve for "a" thusly
6 = a(8 - 4)^2 + 2
6 = a(4)^2 + 2
4 = 16a
a = 1/4
So....our equation is
y = (1/4)(x - 4)^2 + 2 expand and simplify
y = (1/4) [x^2 - 8x + 16] + 2
y = (1/4)x^2 -2x + 4 + 2
y = (1/4)x^2 - 2x + 6 and a = (1/4) , b = -2 and c = 6 ...so ... a + b + c = (1/4) - 2 + 6 = 4 + 1/4 = 17/4
Here's a graph : https://www.desmos.com/calculator/htcmqubuwp