## 5 Conclusions  
This paper aimed to research the MHD flow and heat transfer of hybrid nanofluid on an exponentially shrinking surface with the heat source/sink and thermal radiation effects. After these numerical results were obtained, the behavior on flow and heat transfer in terms of the boundary layer were discovered when involving a few parameters. The results obtained were verified and compared with published results from other studies and the numerical data were found to be almost equivalent with those prior results. These results found that a dual solution exists when \(\lambda>\lambda_{c}\). For the increasing values of \(\varphi_{2}\) and M, the skin friction coefficient, \(f^{\prime\prime}(0)\), as well as the local Nusselt number, \(-\theta^{\prime}(0)\), both increased when the parameter \(\lambda\) was near to the critical value \(\lambda_{c}\). Based on the heat sink/source effect, \(\varepsilon\), the heat transfer rate, \(-\theta^{\prime}(0)\), continues to increase when a heat source exists, \(\varepsilon>0\), whereas there is a reduction in \(-\theta^{\prime}(0)\) when a heat sink exists, \(\varepsilon<0\). The decrease in heat transfer rate, \(-\theta^{\prime}(0)\), is obtained for both solutions when values of the parameter \(Rd\) are increased in a shrinking surface \(\lambda<0\). These results showed that the skin friction coefficient, \(f^{\prime\prime}(0)\), as well as the local Nusselt number, \(-\theta^{\prime}(0)\), both increase more in hybrid nanofluid than in regular nanofluid. Thus, it was confirmed that hybrid nanofluid has better heat transfer enhancement than regular nanofluid. **Author Contributions:** Writing--original draft preparation, M.N.O. ; supervision, writing--review and editing, A.J. ; writing--review and editing N.A.A.B. All authors have read and agreed to the published version of the manuscript. **Funding:** This research was funded by UNIVERSITI KEBANGSAAN MALAYSIA, grant number GGP-2020-030. **Institutional Review Board Statement:** Not applicable. **Informed Consent Statement:** Not applicable. **Data Availability Statement:** Not applicable. **Conflicts of Interest:** The authors declare no conflict of interest. **Nomenclature** \begin{tabular}{l l} \(a\),\(c\) & Stretching/shrinking strength constant \\ \(Bo\) & Magnetic field strength \\ \(C_{f}\) & Skin friction coefficient \\ \(C_{p}\) & Heat capacity \\ \(g\) & Accelerator \\ \(Gr\) & Grashof number \\ \(k\) & Thermal conductivity \\ \(k^{\star}\) & Mean absorption coefficient \\ \(L\) & Characteristics length surface \\ M & Magnetic parameter \\ \(Nu\) & Nusselt number \\ Pr & Prandtl number \\ \(q_{r}\) & Heat flux radiation \\ \(Q\) & Heat source/sink coefficient \\ \(Re\) & Reynold number \\ \(Rd\) & Thermal radiation parameter \\ \(S\) & Mass flux parameter on surface \\ \(T_{w}\) & Surface temperature \\ \(T_{\infty}\) & Ambient temperature \\ \(T_{0}\) & Constant temperature \\ \(u\),\(v\) & Velocity components at x and y axis \\ \(U_{w}\) & Velocity on surface \\ \(v_{w}\) & Mass flux velocity \\ \(x\),\(y\) & Cartesian coordinate \\ Greek Symbols \\ \(\alpha\) & Thermal diffusivity \\ \(\beta\) & Coefficient of thermal expansion \\ \(\eta\) & Similarity independent variable \\ \(f\) & Dimensionless velocity \\ \(\theta\) & Dimensionless temperature \\ \(\lambda\) & Velocity parameter/stretching/shrinking \\ \(\mu\) & Dynamic viscosity \\ \(v\) & Kinematic viscosity \\ \(\varepsilon\) & Heat source/sink \\ \(\rho\) & Density \\ \(\sigma\) & Electrical conductivity \\ \(\sigma^{\star}\) & Stefan--Boltzman constant \\ \(\psi\) & Stream function \\ \(\varphi_{1}\) & Volume fraction of CNTs \\ \(\varphi_{2}\) & Volume fraction of copper \\ \end{tabular}   
* [PERSON] et al. (2020) [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON]; [PERSON] Flow and heat transfer past a permeable power-law deformable plate with orthogonal shear in a hybrid nanofluid. _[PERSON]_**2020**, _59_, 1869-1879. [CrossRef]
* [PERSON] et al.