calculations doesnt fit question

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**broken link removed**
D=30

[latex] 30\ddot{\delta }-\frac{\delta}{3*10^{-9}}=0\\ [/latex]
[latex]x^2=\frac{1}{90*10^{-9}}\\[/latex]
here is the question and soltion of the book

but when i tried to fit the numbers i dont have L in the power of the exponent at all
and other misfits

[latex]x=\pm \sqrt{\frac{1}{90*10^{-9}}}\\[/latex]

[latex]\delta(t)=Ae^{x_1t}+Be^{x_2t}\\[/latex]
[latex]\delta(0)=\delta(L)=9*10^{-8}[/latex]

[latex]x=\pm \sqrt{\frac{1}{90*10^{-9}}}\\[/latex]

[latex]\delta(t)=Ae^{x_1t}+Be^{x_2t}\\[/latex]
[latex]\delta(0)=\delta(L)=9*10^{-8}[/latex]

latex does work for some reason (MOD_EDIT: I FIXED YOUR LATEX)