Tính giá trị biểu thức A = frac2I + 1I + 3 biết I = intlimits_ - 21 left| x

$I = \int\limits_{ - 2}^1 {\left| x \right|} dx = \int\limits_{ - 2}^0 { - xdx} + \int\limits_0^1 x dx = \left. { - \frac{{{x^2}}}{2}} \right|_{ - 2}^0 + \left. {\frac{{{x^2}}}{2}} \right|_0^1 = \left( {0 + \frac{{{{\left( { - 2} \right)}^2}}}{2}} \right) + \frac{1}{2} = \frac{5}{2}.$
Vậy $A = \frac{{2.\frac{5}{2} + 1}}{{\frac{5}{2} + 3}} = \frac{6}{{\frac{{11}}{2}}} = \frac{{12}}{{11}}.$