А) 0,(7)
x=0,777..| *10
10x=7,77
9x=7
x=7/9
Б) 0,(17)
x=0,171717|*100
100x=17,1717
99x=17
x=17/99
В) 0,(045)
x=45/999
Г) 3,6(17)=3+(617-6)/990=3*990+611/990=3581/990
4(a²-2a+1)+6a-a²-12+2a-13= 4a²-8a+4+6a-a²-12+2a-13= 3a²-21
5(a²-8a+16)-7a+a²+28-4a-18a+6= 5a²-40a+80-7a+a²+28-4a-18a+6= 6a²-69a+114
Sinx*Cosy+Siny*Cosx-Sinx*Cosy+Siny*Cosx/
/Cosx*Cosy-Sinx*Siny+Cosx*Cosy+Sinx*Siny=
2Siny*Cosx/2Sinx*Siny=Cosx/Sinx=Ctgx