[tex]\text{Vectorii }\overrightarrow{v}=a_1\cdot \overrightarrow{i}+b_1\cdot \overrightarrow{j}\ \text{si}\ \overrightarrow{y}=a_2\cdot \overrightarrow{i}+b_2\cdot \overrightarrow{j}\text{ sunt coliniari}\\
\text{daca si numai daca }\dfrac{a_1}{a_2}=\dfrac{b_1}{b_2}\\
\text{In cazul nostru vom avea:}\\
\dfrac{2}{a+3}=\dfrac{a}{2}\\
a^2+3a=4\\
a^2+3a-4=0\\
(a+4)(a-1)=0\Rightarrow a_1=1\\
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~a_2=-4\ \textless \ 0(\text{nu convine})\\
\text{Deci a=1.}[/tex]
