√6*cos(π-π/4)*sin(π+π/3)=√6*(-cosπ/4)*(-sinπ/3)=√6*√2/2*√3/2=1,5
6tg(180+45)*(-sin30)=-6*tg45*1/2=-3*1=-3
4tg(3π+π/3)*tg(3π-π/6)=4*tgπ/3*(-tgπ/6)=-4*√3*1/√3=-4
по формуле разности квадратов:
х²у² - 4/9 = (ху - 2/3)(ху + 2/3)
(a+b)²=a²+2ab+b²=a² + 2ab +b²-2ab+2ab=(a²-2ab+b²)+4ab=(a-b)²+4ab= 7²+4*(-4)= 49-16=33