5x-7(x-3)=4x+5
5х-7х+21= 4х+5
5х-7х-4х = -21+5
-6х = -16
х = 16/6
х = 2 4/6
3(x-2)=5x+3
3х -6 = 5х+3
3х -5х = 3+6
-2х = 9
х = -9/2
х = - 4 1/2
0,3^-2+(3/7)^-1+(-0,5)^-2*(3/4)+(-1)^-8*6=100/9+7/3+4*(3/4)+6=100/9+7/3+9=22 целых 4/9
(2/3)^-2-(1/9)^-1+(6/17)^0*(1/8)-0,25^-2*16=9/4-9+1/8-16*16=19/8-265=-262 целых 3/8
Cos п/6 = √3/2
ctg п/3 = 1/√3
ctg 9п/4 не определен
√3*√3/2+√3*1/√3=3/2+√3/√3=3/2+1=2,5