Question

\(5\sin x-6\cos^2x=13\)

Answer 1

\(5sinx-6\left(1-sin^2x\right)=13\)

\(\Leftrightarrow5sinx-6-6sin^2x=13\)

\(\Leftrightarrow5sinx-19-6sin^2x=0\)

bấm máy tính giải ra nghiệm

Answer 2

\(\Leftrightarrow5sinx-6\left(1-sin^2x\right)=13\)

\(\Leftrightarrow5sinx-6+6sin^2x-13=0\)

=>\(6sin^2x+5sinx-19=0\)

hay \(x\in\varnothing\)