Đáp án: P=3
Giải thích các bước giải:
$\eqalign{ & a)\,P = \frac{{2x}}{{2x + 3}} - \frac{1}{{2x - 3}} - \frac{{4x - 12}}{{9 - 4{x^2}}} \cr & = \frac{{2x(2x - 3)}}{{(2x + 3)(2x - 3)}} - \frac{{2x + 3}}{{(2x + 3)(2x - 3)}} + \frac{{4x - 12}}{{(2x + 3)(2x - 3)}} \cr & = \frac{{4{x^2} - 6x - 2x - 3 + 4x - 12}}{{(2x + 3)(2x - 3)}} \cr & = \frac{{4{x^2} - 4x - 15}}{{(2x + 3)(2x - 3)}} \cr & = \frac{{(2x + 3)(2x - 5)}}{{(2x + 3)(2x - 3)}} \cr & = \frac{{2x - 5}}{{2x - 3}} \cr} $
$b)\,P = \frac{{2x - 5}}{{2x - 3}}$
Khi x=1 thì
$\,P = \frac{{2.1 - 5}}{{2.1 - 3}} = \frac{{ - 3}}{{ - 1}} = 3$
