Question

(-4+3)x(2-1)=-1 but what's the algorithm to that? I don't get it

Answer 1

Use the property called FOIL.
First Outer Inner Last
\[(-4+3)\times(2-1) \implies -8 + 4 + 6 - 3\]
\[-4 + 6 - 3 \implies 2 - 3\implies -1\]