Cho hình vuông $ABCD$ cạnh $a$, tâm $O$. Khi đó: $\left| {\overrightarrow {OA} - \overrightarrow {BO} } \right| =$

$\emptyset$

$\left[ {0;5} \right]$

$\left[ {3;4} \right]$

$\left\{ {3;4} \right\}$

$a > 0,\,\,b < 0,\,\,c > 0$

$a < 0,\,\,b > 0,\,\,c > 0$

$a < 0,\,\,b < 0,\,\,\,c < 0$

$a < 0,\,\,b < 0,\,\,c > 0$

$2\overrightarrow {GM}$.

$\dfrac{2}{3}\overrightarrow {GM}$.

$- \dfrac{2}{3}\overrightarrow {AM}$.

$\dfrac{1}{2}\overrightarrow {AM}$.

$y =  - {\left( {x + 1} \right)^2}$.

$y =  - {\left( {x - 1} \right)^2}$.

$y = {\left( {x + 1} \right)^2}$.

$y = {\left( {x - 1} \right)^2}$.

$\left( {0;3} \right)$. 

$\left( {\dfrac{1}{3};0} \right)$.

$\left( {0;2} \right)$.

$\left( {4;2} \right)$.

$\{ 3;5\}$

$\{ 1;{\rm{ }}3;{\rm{ }}5;{\rm{ }}7;{\rm{ }}8;{\rm{ }}9\}$ .

$\{ 1;{\rm{ }}7;{\rm{ }}9\} .$          

$\{ 1;{\rm{ }}3;{\rm{ }}5\} .$