[tex]\text{Vom folosi conditia de coliniaritate a doi vectori.}\\\text{Vectorii }\vec{v}=a_1\cdot \vec{i}+b_1\cdot \vec{j}\text{ si }\vec{u}=a_2\cdot \vec{i}+b_2\cdot \vec{j}\text{ sunt coliniari,daca si numai}\\\text{ daca }\boxed{\dfrac{a_1}{a_2}=\dfrac{b_1}{b_2}}\\\text{Aplicam formula si pentru cazul de fata:}\\\dfrac{a+2}{5}=\dfrac{2a-9}{-3}\\-3(a+2)=5(2a-9)\\-3a-6=10a-45\\13a=39\\\boxed{a=3}[/tex]
