#### Answer

$$ y=20e^{\sqrt{2}t}.$$

#### Work Step by Step

The solution of the differential equation is given by
$$ y=Ce^{\sqrt{2}t}.$$
To find $ C $, we use the initial condition $ y(0)=20$, then we have $ C=20$.
Hence the solution is
$$ y=20e^{\sqrt{2}t}.$$