\[\boxed{\mathbf{978\ (968).}\mathbf{\ }Еуроки\ - \ ДЗ\ без\ мороки}\]
\[1)\ a = - 3;\ \ b = - 7:\]
\[|a| + |b| = | - 3| + | - 7| =\]
\[= 3 + 7 = 10\]
\[|a + b| = | - 3 - 7| = | - 10| = 10\]
\[2)\ a = - 4;\ \ b = 10:\]
\[|a| + |b| = | - 4| + |10| =\]
\[= 4 + 10 = 14\]
\[|a + b| = | - 4 + 10| = |6| = 6\]
\[3)\ a = 7,2;\ \ b = 2,8:\]
\[|a| + |b| = |7,2| + |2,8| =\]
\[= 7,2 + 2,8 = 10\]
\[|a + b| = |7,2 + 2,8| = 10\]
\[Чтобы\ выполнялось\ равенство\]
\[\ |a| + |b| = |a + b|;\]
\[числа\ \text{a\ }и\ \text{b\ }должны\ быть\ \]
\[одного\ знака.\]