1、√（- 4）× （- 9）
= √ 4 × 9
= √ 36
= √ 6 ²
= 6
2、﹣6√45 ×﹙﹣4√48﹚
= - 6 × （- 4）× √ 45 × 48
= 24 × √ 5 × 9 × 3 × 16
= 24 × √ 3 ² × 4 ² × 15
= 24 × 3 × 4 × √ 15
= 288 √ 15