What is $2a+3b$, where $a=2-i$ and $b=-1+i$?
To simplify $2a+3b$, I need to plug in the given values of $a$ and $b$ and combine like terms. So, $2a+3b=2(2-i)+3(-1+i)$. Multiplying out the brackets, I get $4-2i-3+3i$. Adding up the real and imaginary parts, I get $1+i$. 