[" The length of a metal wire is "l_(1)" when the tension in it is "T_(1)" and is "l_(2)" when the tension is "T_(2).T],[" natural length of the wire is "],[[" (a) "(l_(1)+l_(2))/(2)," (b) "sqrt(l_(1)l_(2))," (c) "(l_(1)T_(2)-l_(2)T_(1))/(T_(2)-T_(1))," (d) "(l_(1)T_(2)+l_(2)T_(1))/(T_(2)+T_(1))]]