For each of the exercises given below,verify that the given function (implicit or explicit) is a solution of the corresponding differential equation.
$y=e^{x}(a \cos x+b \sin x) \quad: \frac{d^{2} y}{d x^{2}}-2 \frac{d y}{d x}+2 y=0$

(N/A) Given function: $y=e^{x}(a \cos x+b \sin x) = ae^{x} \cos x + be^{x} \sin x$.
Differentiating with respect to $x$:
$\frac{dy}{dx} = a(e^{x} \cos x - e^{x} \sin x) + b(e^{x} \sin x + e^{x} \cos x)$
$\frac{dy}{dx} = e^{x}[(a+b) \cos x + (b-a) \sin x]$.
Differentiating again with respect to $x$:
$\frac{d^{2}y}{dx^{2}} = \frac{d}{dx} \{e^{x}[(a+b) \cos x + (b-a) \sin x]\}$
$\frac{d^{2}y}{dx^{2}} = e^{x}[(a+b) \cos x + (b-a) \sin x] + e^{x}[-(a+b) \sin x + (b-a) \cos x]$
$\frac{d^{2}y}{dx^{2}} = e^{x}[(a+b+b-a) \cos x + (b-a-a-b) \sin x]$
$\frac{d^{2}y}{dx^{2}} = e^{x}[2b \cos x - 2a \sin x]$.
Substituting $\frac{d^{2}y}{dx^{2}}$,$\frac{dy}{dx}$,and $y$ into the $L.H.S.$ of the differential equation:
$L.H.S. = \frac{d^{2}y}{dx^{2}} - 2\frac{dy}{dx} + 2y$
$= e^{x}[2b \cos x - 2a \sin x] - 2e^{x}[(a+b) \cos x + (b-a) \sin x] + 2e^{x}[a \cos x + b \sin x]$
$= e^{x}[2b \cos x - 2a \sin x - 2a \cos x - 2b \sin x + 2b \sin x - 2a \cos x + 2a \cos x + 2b \sin x]$
$= e^{x}[(2b - 2a - 2b + 2a) \cos x + (-2a - 2b + 2b + 2a) \sin x]$
$= e^{x}[0 \cos x + 0 \sin x] = 0 = R.H.S.$
Thus,the given function is a solution of the differential equation.