1
9b+(5a-9b²)/b=(9b²+5a-9b²)/b=5a/b
a=9 b=36 45/36=5/4=1.25
2
1)(a+2b)/[a(a-2b)]-1/a=(a+2b-a+2b)/[a(a-2b)]=4b/[a(a-2b)]
2)4b/[a(a-2b)]*(2b-a)/b=-4/a
a=1,6 -4/1,6=-2,5
3
8a/9c-(64a²+81c²)/72ac+(9c-64a)/8a=
=(64a²-64a²-81c²+81c²-64a*9c)/72ac=-64a*9c/72ac=-8
4
[(3x+7)²-(3x-7)²]/x=(3x+7-3x+7)(3x+7+3x-7)/x=14*6x/x=84