第一个：3.6-3.6×0.5
=3.6×(1-0.5)
=3.6×0.5
=1.8
第二个：5.8×5.8+0.58×42+58
=5.8×5.8+5.8×0.1×42+58
=5.8×5.8+5.8×4.2+58
=5.8×(5.8+4.2)+58
=5.8×10+58
=58+58
=116