初三(上)二次根式的乘除...高人来指点下啊.

1.根号6X (-根号15)
=-根号(6*15)
=-3根号10

2.根号3平方X 4的3次方X 5
=3*4根号(4*5)
=12*2根号5
=24根号5

3.2根号S平方Y除以3根号SY
=(2/3)根号S

4.根号4C的平方除以A的平方B
=(2C/(AB))根号B

5.根号27X根号50／根号6
=根号(27*50/6)
=根号(9*25)
=3*5
=15

6.根号0.4X根号3.6
=根号(0.4*3.6)
=根号(4*0.36)
=2*0.6
=1.2

直接乘呀
比如第六个6.根号0.4X根号3.6，根号下面0.4X3.6
上面几个上不懂写的是什么

1.根号6X (-根号15)
=√6*(-√15)
=-√90
=-3√10

2.根号3平方X 4的3次方X 5.
=(√3)^2*4^3*5
=3*64*5
=960

3.2根号S平方Y除以3根号SY
=2(√s)^2y/√3sy
=2sy/√3sy
=2/√3
=2√3/3

4.根号4C的平方除以A的平方B

=√(4c^2)/a^2b
=2c/a^2b

5.根号27X根号50／根号6
=√27*√50/√6
=3√3*5√2/√6
=15√6/√6
=15

6.根号0.4X根号3.6

=√0.4*√3.6
=√2/5*√36/10
=√72/50
=√36/25
=6/5

1.负号提出来，根号A*根号B 等于根号（A*B）故得-根号90 ，又因为90=3×3×2×10所以3平方可以开出来，就得-3又根号10
2.是这样吗？根号（3平