8cos²x-2sinxcosx-3=0
8cos²x-2sinxcosx-3*1=0
8cos²x-2sinxcosx-3(sin²x+cos²x)=0
8cos²x-2sinxcosx-3sin²x-3cos²x=0
5cos²x-2sinxcosx-3sin²x=0
5-2tgx-3tg²x=0
5-2t-3t²=0
3t²+2t-5=0
(t-1)(3t+5)=0
t1=1
t2=-5/3
tgx=1
tgx=-5/3
x1=П/4+Пn, n€Z
x2=arctg(-5/3)+Пk, k€Z
.........................................................................................
3+5/6=5,75*|х|;
|х|=(23/6)/(23/4)=2/3;
ответ х1=2/3, х2=-2/3.
(3,7-x):0,36=1,05
x=3,7-0,36*1,05
x=3,322