Help Maths- The circle

The circle C, with centre at the point A, has equation x2 + y2-10x+ 9= 0

a. find the coordinates of A
b. the radius of C
c. the coodinates of the points at which C crosses the x-axis.
d. Given that the line L with gradient 7/2 is a tangent to C, and that L toughes C at the point T , find an equation of the line which passes through A and T
(a)
From x^2 + y^2-10x+ 9= 0
(x-5)^2+(y-0)^2=16
The coordinates of A is (5,0)
(b)
the radius of C=4
(c)
set y=0
(x-5)^2=16
x-5=4 or -4
x=9 or 1
the coodinates of the points at which C crosses the x-axis are
(9,0) or (1,0)
(d)
The slope of the line L1 which passes through A and T should be perpendicular to the line L
So the slope of L1=-2/7
Using point-slope form
(y-0)/(x-5)=-2/7
-2x+10=7y
2x+7y-10=0