3sin^2x+sinx cosx -4cos^2x=0

3sin²x+sinxcosx-4cos²x=03tg²x+tgx-4=0tgx=a3a²+a-4=0D=49a=1;tgx=1⇒x=π/4+πna=-4/3; tgx=-4/3⇒x=-arctg4/3+πk