Hi
Note: Standard Form of an Equation of a Circle is 
where Pt(h,k) is the center and r is the radius
||Vertex(0,0), radius of 5
line that is tangent to the circle 25= x^2+y^2 at the point (3,4)
(3,4)
(0,0) m = 4/3, which is the slope of the radius, slope of the tangent line = -(3/4)
y = (-3/4)x + b
4 = (-3/4)3 + b, b = 25/4 and y = (-3/4)x + 25/4
See below descriptions of various conics
Standard Form of an Equation of a Circle is
where Pt(h,k) is the center and r is the radius
Standard Form of an Equation of an Ellipse is 
where Pt(h,k) is the center. (a positioned to correspond with major axis)
a and b are the respective vertices distances from center and ±
are the foci distances from center: a > b
Standard Form of an Equation of an Hyperbola opening right and left is:
where Pt(h,k) is a center with vertices 'a' units right and left of center.
Standard Form of an Equation of an Hyperbola opening up and down is:
where Pt(h,k) is a center with vertices 'b' units up and down from center.
the vertex form of a parabola opening up or down, 
where(h,k) is the vertex.
The standard form is 
, where the focus is (h,k + p)
the vertex form of a parabola opening right or left, 
where(h,k) is the vertex.
The standard form is 
, where the focus is (h +p,k )
