1.当M＞0,N＞0,C＜0时.√49m^2n/9c^2=( )

1.当M＞0,N＞0,C＜0时.√49m^2n/9c^2=(-7m√n/3c )

2.化简:
(1)
√5a^3b/(a-b)^2 (a＞b)
=√[5ab*a^2/(a-b)^2]
=a/(a-b)*√(5ab)

(2)
√x^3+4x^2+4x/y^2+6y+9 (x＞0,y＞-3)
=√[x(x^2+4x+4)/(y+3)^2]
=√[x(x+2)^2/(y+3)^2]
=(x+2)/(y+3)*√x

(3)
√a^3-4a^2b+4ab^2 (a＞2b)
=√[a(a^2-4ab+4b^2)
=√[a(a-2b)^2
=(a-2b)√a

(4)
2a^2/3b√b^3/a^4-b^2/a^4 (b＞1)
=2a^2/3b*√[b^2/a^4(b-1)]
=2a^2/3b*b/a^2*√(b-1)
=2/3√（b-1)