Интеграл от 3 до а. dx/(3+x)^2=1/30 Найти значение а.

[latex] \int\limits^a_3 { \frac{1}{(x+3)^2} } \, dx = \frac{1}{30} [/latex] [latex] \int\limits^a_3 {{(x+3)^{-2}} \, d(x+3) = \frac{1}{30} [/latex] [latex]\frac{1}{-2+1}*(x+3)^{-2+1}|_3^a=\frac{1}{30} [/latex] [latex]\frac{1}{-1}*(x+3)^{-1}|_3^a=\frac{1}{30} [/latex] [latex]\frac{1}{x+3}|_3^a=-\frac{1}{30}[/latex] [latex]\frac{1}{a+3}- \frac{1}{3+3}=-\frac{1}{30}[/latex] [latex]\frac{1}{a+3}=\frac{1}{6}-\frac{1}{30}[/latex] [latex]\frac{1}{a+3}=\frac{1}{6}(1-\frac{1}{5})[/latex] [latex]\frac{1}{a+3}=\frac{1}{6}*\frac{4}{5}[/latex] [latex]\frac{1}{a+3}=\frac{1}{\frac{6*5}{4}}[/latex] [latex]a+3=\frac{6*5}{4}[/latex] [latex]a+3=7.5[/latex] [latex]a=4.5[/latex]