1) a)7-9=-2
б) sqrt(16/9)-sqrt(25/4)=4/3-5/2=-7/6
в) 3*2sqrt(5)+5*3sqrt(5)-2*4*sqrt(5)=sqrt(5)(6+15-8)=13sqrt(5)
2) x(6-5x)=0 x=0 x=1,2
0,6x^2=0,3 x^2=1/2 x=sqrt(2)/2 x=-sqrt(2)/2
x=(13+-sqrt(169-168))/6=(13+-1)/6 x1=2 x2=7/3
x-2=t
t^2-5t+4=0
t1=4 t2=1
x-2=1 x=3
x-2=4 x=6