Question

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

Answer 1

3sin²x+sinxcosx-4cos²x=0
3tg²x+tgx-4=0
tgx=a
3a²+a-4=0
D=49
a=1;tgx=1⇒x=π/4+πn
a=-4/3; tgx=-4/3⇒x=-arctg4/3+πk