Two solutions to $y^{\text{'}\text{'}}+7y^{\text{'}}+6y=0$ are $y_1=e^{-4t},y_2=e-$t$.$

a$)$ Find the Wronskian.

$W$

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b$)$ Find the solution satisfying the initial conditions $y(0)=6,y^{\text{'}}(0)=-31$

$y=$

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