Persmaan garis singgung di titik(-3,4) ada lingkaran x2+y2+2x-10y+21=0adaalh

[tex]x^2+y^2+2x-10y+21=0\\ \\ (x^2+2x+1)-1+(y^2-10y+25)-25+21=0\\ \\ (x+1)^2+(y-5)^2=5\\ \\ P(-1,5)\ dan\ r^2=5\\ \\ persamaan\ garis\ singgung\ lingkaran:\\ (x-a)(x_1-a)+(y-b)(y_1-b)=r^2\\ \\ (x-(-1))(-3-(-1))+(y-5)(4-5)=5\\ \\ (x+1)(-2)+(y-5)(-1)=5\\ \\ -2x-2-y+5=5\\ \\ -2x-y=2\\ \\ 2x+y+2=0[/tex]

Titik singgung (x1, y1)=(-3, 4)

PGS lingkaran:
x1.x + y1.y + 2(x1 + x)/2 -10(y1 +y)/2 + 21 = 0
-3x + 4y + (-3 + x) -5(4 + y) + 21 = 0
-3x + 4y - 3 + x - 20 - 5y + 21 = 0
-2x - y - 2 = 0
2x + y + 3 = 0