Answer:
a). Center of the circle = (-2, 5)
b). Equation of the line ⇒ y = ![-\frac{4}{5}x+\frac{58}{5}](https://tex.z-dn.net/?f=-%5Cfrac%7B4%7D%7B5%7Dx%2B%5Cfrac%7B58%7D%7B5%7D)
Step-by-step explanation:
Equation of the circle is,
x² + 4x + y²- 10y + 20 = 30
a). [x² + 2(2)x + 4 - 4] + [y²- 2(5)y + 25] - 25 + 20 = 30
[x² + 2(2)x + 4] - 4 + [y² - 2(5)y + 25] - 25 + 20 = 30
(x + 2)² + (y - 5)²- 29 + 20 = 30
(x + 2)² + (y - 5)²- 9 = 30
(x + 2)² + (y - 5)² = 39
By comparing this equation with the standard equation of a circle,
Center of the circle is (-2, 5).
b). A point (2, 10) lies on this circle.
Slope of the line joining this point to the center (-2, 5),
![m_{1}=\frac{y_{2}-y_{1}}{x_{2}-x_{1}}](https://tex.z-dn.net/?f=m_%7B1%7D%3D%5Cfrac%7By_%7B2%7D-y_%7B1%7D%7D%7Bx_%7B2%7D-x_%7B1%7D%7D)
= ![\frac{10-5}{2+2}](https://tex.z-dn.net/?f=%5Cfrac%7B10-5%7D%7B2%2B2%7D)
= ![\frac{5}{4}](https://tex.z-dn.net/?f=%5Cfrac%7B5%7D%7B4%7D)
Let the slope of the tangent which is perpendicular to this line is '
'
Then by the property of perpendicular lines,
![m_{1}\times m_{2}=-1](https://tex.z-dn.net/?f=m_%7B1%7D%5Ctimes%20m_%7B2%7D%3D-1)
![\frac{5}{4}\times m_{2}=-1](https://tex.z-dn.net/?f=%5Cfrac%7B5%7D%7B4%7D%5Ctimes%20m_%7B2%7D%3D-1)
![m_{2}=-\frac{4}{5}](https://tex.z-dn.net/?f=m_%7B2%7D%3D-%5Cfrac%7B4%7D%7B5%7D)
Now the equation of the line passing though (2, 10) having slope ![m_{2}=-\frac{4}{5}](https://tex.z-dn.net/?f=m_%7B2%7D%3D-%5Cfrac%7B4%7D%7B5%7D)
y - y' = ![m_{2}(x-x')](https://tex.z-dn.net/?f=m_%7B2%7D%28x-x%27%29)
y - 10 = ![-\frac{4}{5}(x-2)](https://tex.z-dn.net/?f=-%5Cfrac%7B4%7D%7B5%7D%28x-2%29)
y - 10 = ![-\frac{4}{5}x+\frac{8}{5}](https://tex.z-dn.net/?f=-%5Cfrac%7B4%7D%7B5%7Dx%2B%5Cfrac%7B8%7D%7B5%7D)
y = ![-\frac{4}{5}x+\frac{8}{5}+10](https://tex.z-dn.net/?f=-%5Cfrac%7B4%7D%7B5%7Dx%2B%5Cfrac%7B8%7D%7B5%7D%2B10)
y = ![-\frac{4}{5}x+\frac{58}{5}](https://tex.z-dn.net/?f=-%5Cfrac%7B4%7D%7B5%7Dx%2B%5Cfrac%7B58%7D%7B5%7D)
Therefore, equation of the line will be, y = ![-\frac{4}{5}x+\frac{58}{5}](https://tex.z-dn.net/?f=-%5Cfrac%7B4%7D%7B5%7Dx%2B%5Cfrac%7B58%7D%7B5%7D)