## Thomas' Calculus 13th Edition

$(-6i-9j)+(7i+7j)$
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 $a(2i+3j)+b(i+j)=-3(2i+3j)+7(i+j)=(-6i-9j)+(7i+7j)$