Nếu \(\sin x+\cos x=\dfrac{1}{2}\) thì \(3\sin x+2\cos x=?\)
\(\dfrac{7-\sqrt{5}}{4}\) hay \(\dfrac{7+\sqrt{5}}{4}\).\(\dfrac{5-\sqrt{7}}{4}\) hay \(\dfrac{5+\sqrt{7}}{4}\).\(\dfrac{2-\sqrt{3}}{5}\) hay \(\dfrac{2+\sqrt{3}}{5}\).\(\dfrac{3-\sqrt{2}}{5}\) hay \(\dfrac{3+\sqrt{2}}{5}\).Hướng dẫn giải:Từ \(\sin x+\cos x=\dfrac{1}{2}\) và \(\sin^2x+\cos^2x=1\)
