Question

Answer 1

`[-x^2-x+2]/[-x^2+2x] <= 0`      `(**)`     `ĐK: x \ne 0,x \ne 2`

Xét: `-x^2-x+2=0<=>`$\left[\begin{matrix} x=-2\\ x=1\end{matrix}\right.$

      `-x^2+2x=0<=>`$\left[\begin{matrix} x=0\\ x=2\end{matrix}\right.$

BXD:

\begin{array}{|c|cc|}\hline x&-\infty & &-2&&0&&1&&2&&+\infty\\\hline -x^2-x+2 & &-& 0&+&|&+&0&-&|&-\\\hline -x^2+2x& &-&|&-&0&+&|&+&0&-\\\hline VT(*)&&+&0&-&||&+&0&-&||&+\\\hline\end{array}

   `VT(**) <= 0<=>x in [-2;0) uu [1;2)`

KL: Bpt có tập nghiệm `[-2;0) uu [1;2)`