А4=а1+3d=4
a12=a1+11d=36
a1=4-3d
4-3d+11d=36
4+8d=36
8d=32
d=4
a1=4-3*4
a1=-8
Tg(3x+1)=1
3x+1=π/4+πn
3x=-1+π/4+πn
x=-1/3+π/12+πn/3,n∈z
9х-6x+6xy-9y=3x-3xy(во второй степени)=х(во2 степени)у(во 2 степени)
( 7•1/3 )/ ( 3•1/3 - 2 ) = 7/3 : ( - 1 ) = - 7/3
( 2•1/3 + 5 )/ ( 2•1/3 - 1 ) = ( 2/3 + 15/3 ) / ( 2/3 - 3/3 ) = 17/3 : ( - 1/3 ) = - 17
- 7/3 + 17 = - 2 1/3 + 16 3/3 = 14 2/3