persamaan garis singgung lingkaran a) x²+y²=4 dititik (-5,4) b) (x+3)² +(y-5)²=9 dititik (-4,7)

a) x1.x + y1.y = r²
-5x + 4y = 4
-5x + 4y - 4 = 0

b) (x1 - a)(x - a) + (y1 - b)(y - b) = r²
(-4 + 3)(x + 3) + (7 - 5)(y - 5) = 9
-1(x + 3) + 2(y - 5) = 9
-x - 3 + 2y - 10 = 9
-x + 2y - 3 - 10 - 9 = 0
-x + 2y - 22 = 0