Activity: Equation of a circle is x² + y² = 9. Its centre is at (.) and radius is [ Equation of a line is 3x - 4y +15=0 x+0 Comparing it with y = mx + c :y= and c = m = We know that, if the line y = mx +c is a tangent to x² + y² = a² then c² = a²m² + a² Also, c²=a²m² +a² = 9 +9 Hence c² = ( )² 225 16 = **** = 9 9 16 = 9(25) 16 225 .(II) 16 From equations (I) and (II) we conclude that​