Fixed typo in exponential model.

src/de/tud/kom/p2psim/impl/topology/views/fiveg/models/ExponentialModel.java

@@ -65,7 +65,7 @@ public class ExponentialModel extends AbstractModel {
 	
 	@Override
 	public String toString() {
-		return "Exponential Model: exp(u) = " + this.a + " * e^(" + this.c + " * (u + " - this.d + ")) + " + this.b;
+		return "Exponential Model: exp(u) = " + this.a + " * e^(" + this.c + " * (u - " + this.d + ")) + " + this.b;
 	}
 
 }