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[latex]y''+121y=9x+11\\\\1)\quad y''+121y=0\\\\\lambda ^2+121=0\; ,\; \lambda _{1,2}=\pm 11i\\\\y_{obshee\; odnorodn.}=C_1\cdot cos11x+C_2\cdot sin11x\\\\2)\quad Vid\; chastnogo\; reshtniya:\; \; y_{ch.resh.}=Ax+B\\\\y'_{ch.resh.}=A\\\\y''_{ch.resh.}=0\\\\------------------------\\\\y''_{ch.resh.}+121y_{ch.redh.}}=0+121(Ax+B)=9x+11\\\\121Ax+121B=9x+11\\\\121A=9\; \; \to \; \; A=\frac{9}{121}\\\\121B=11\quad \to \; \; \; B=\frac{1}{11}\\\\y_{ch.resh.}=\frac{9}{121}x+\frac{1}{11}[/latex]
[latex]3)\; \; \; y_{obsh.neodnor.}=C_1\cdot cos11x+C_2\cdot sin11x+\frac{9}{121}x+\frac{1}{11}[/latex]
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