а) 2 * 7 - 3 * 5 = 14 - 15 = -1
б) 2/3 * 60 = 40
в) 3 * 8/9 = 8/3 = 2 2/3
г) 10 * 9/5 - 16 = 18 - 16 = 2
1) х1+х2=-b/a
sin(π/4-a)+cos(π/4-a) sin(π/4-a)+sin(π/4+a) 2sinπ/4 cosa