#### Answer

$(-6i-9j)+(7i+7j)$

#### Work Step by Step

Let us consider that $u=u_1+u_2$
and $i-2j=a(2i+3j)+b(i+j)$ ...(1)
Equate the terms, we get, $2a+b=1; 3a+b=-2$
Need to solve these two equations, so that $a=-3$
Also, $2a+b=-1$
or, $(2)(-3)+b=1$
Thus, $b=7$
From equation (1), we have $a(2i+3j)+b(i+j)=-3(2i+3j)+7(i+j)=(-6i-9j)+(7i+7j)$