To multiply \(-49\) by \(99\):

\[
-49 \times 99 = -49 \times (100 - 1)
\]

Using the distributive property:

\[
-49 \times 100 - (-49 \times 1)
\]

Calculate each part:

\[
-49 \times 100 = -4900
\]
\[
-49 \times 1 = -49
\]

So,

\[
-4900 - (-49) = -4900 + 49 = -4851
\]

Therefore,

\[
-49 \times 99 = -4851
\]