fskilnik@GMATH wrote:GMATH practice exercise (Quant Class 20)
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$$? = {y_C}$$
$$\left( {1 + 2} \right)\,\,\,\left\{ \matrix{
\,OD = 2\sqrt 2 \hfill \cr
\Delta AOB\,\,{\rm{isosceles}} \hfill \cr} \right.\,\,\,\,\,\, \Rightarrow \,\,\,\,\,\left\{ \matrix{
\,\Delta ODB\,\,{\rm{isosceles}} \hfill \cr
\,BD = OD\,\,,\,\,OB = 4 \hfill \cr} \right.\,\,\,\,\,\, \Rightarrow \,\,\,\,\,\left\{ \matrix{
\,\Delta BEF\,\,{\rm{isosceles}} \hfill \cr
\,FG = GB = 4 - 3 \hfill \cr} \right.$$
$$\,\, \Rightarrow \,\,\,{\rm{line}}\,\,EC\,\,\,\left\{ \matrix{
\,{\rm{slope}} = 1\,\,\,\left( {{{45}^ \circ }} \right) \hfill \cr
\,F = \left( {2,0} \right) \in \,\,{\rm{line}} \hfill \cr} \right.\,\,\,\,\,\,\,\, \Rightarrow \,\,\,\,\,\,{\rm{line}}\,\,EC\,\,{\rm{unique}}\,\,\,\,\,\, \Rightarrow \,\,\,\,\,\,C\,\,{\rm{unique}}\,\,\,\,\,\, \Rightarrow \,\,\,\,\,{\rm{SUFF}}.$$
The correct answer is (C).
We follow the notations and rationale taught in the GMATH method.
Regards,
Fabio.
