Giải thích các bước giải:
\(\begin{array}{l}
Xet\,pt\,hoanh\,do\,giao\,diem\\
{x^2} - 2mx + {m^2} = x - 1\\
\Leftrightarrow {x^2} - \left( {2m - 1} \right)x + {m^2} + 1 = 0\\
\Delta = {\left( {2m - 1} \right)^2} - 4\left( {{m^2} + 1} \right)\\
= - 4m - 3 > 0 \Leftrightarrow m < - \dfrac{3}{4}\\
P\left( {{x_1};{x_1} - 1} \right),Q\left( {{x_2};{x_2} - 1} \right)\\
\Rightarrow PQ = \sqrt {2{{\left( {{x_1} - {x_2}} \right)}^2}} = \sqrt {2{{\left( {{x_1} + {x_2}} \right)}^2} - 8{x_2}{x_1}} \\
\Leftrightarrow 2{\left( {{x_1} + {x_2}} \right)^2} - 8{x_1}{x_2} = 9\\
\Leftrightarrow 2\left( { - 4m - 3} \right) = 9\\
\Leftrightarrow - 8m - 15 = 0 \Leftrightarrow m = - \dfrac{{15}}{8}\left( {tm} \right)
\end{array}\)
