Answer
$e^{4x}$
Work Step by Step
Use hyperbolic functions formula as follows: $ \cosh x= \dfrac{e^x+e^{-x}}{2}$ and $ \sinh x= \dfrac{e^x-e^{-x}}{2}$
Need to solve :$(\sinh x + \cosh x)^4$
This implies, $(\sinh x + \cosh x)^4=[\dfrac{e^x-e^{-x}}{2}+\dfrac{e^x+e^{-x}}{2}]^4=[\dfrac{2e^x}{2}]^4$
Hence, $(\sinh x + \cosh x)^4=e^{4x}$
