Abstract
We show that the Benjamin-Bona-Mahoney (BBM) equation with power law nonlinearity can be transformed by a point transformation to the combined KdV-mKdV equation, that is also known as the Gardner equation. We then study the combined KdV-mKdV equation from the Lie group-theoretic point of view. The Lie point symmetry generators of the combined KdV-mKdV equation are derived. We obtain symmetry reduction and a number of exact group-invariant solutions for the underlying equation using the Lie point symmetries of the equation. The conserved densities are also calculated for the BBM equation with dual nonlinearity by using the multiplier approach. Finally, the conserved quantities are computed using the one-soliton solution. (C) 2012 Elsevier Ltd. All rights reserved.