salah satu persamaan garis singgung lingakaran x² + y² + 4x + 2y - 20 = 0 yang sejajar garis 3x +4y = 7

x² + y² + 4x + 2y - 20 = 0
(x+2)² + 4 + (y+1)² +1 -20 = 0
(x+2)² + (y+1)² = 20-4-1
(x+2)² + (y+1)² = 15

m = -x/y = -3/4
r² = 15
r = √15
y-y1 = m(x-x1) ± r√1+m²
y+1 = -3/4(x+2) ± √15√1+(-3/4)²
y+1 = -3/4x - 3/2 ± √15√1+(9/16)
y+1 = -3/4x - 3/2 ± √15.√25/16
y+1 = -3/4x -3/2 ± √15(5/4)
4y + 4 = -3x -6 ± 5√15