А) 12х-7 = 12*0,05-7 = 0,6-7 = -6,4
б) 3-1,5х = 3-1,5*(-1/3) = 3-3/2*(-1/3) = 3+1/2 = 3 1/2 = 3,5
в) (2х-у):(х-3у) = (2*(-1)-1/3):(-1-3*1/3) =
-2 1/3:(-2) = -7/3*(-1/2) = 7/6 = 1 1/6
(5a+5b)-(ax+bx)=5(a+b)-x(a+b)=(a+b)(5-x).
25x²-10xy+y²-9=(25x²-10xy+y²)-9=(5x-y)²-3²=(5x-y-3)*(5x-y+3)
Sina=12/13, tga=12/5, ctga=5/12