Question

tìm min,max y=2 căn(cos3x)-1

Answer 1

\(y=2\sqrt{cos3x-1}\) hay \(y=2\sqrt{cos3x}-1\) em nhỉ?

Answer 2

Ta có:

\(0\le\sqrt{cos3x}\le1\)

\(\Rightarrow0\le2\sqrt{cos3x}\le2\)

\(\Rightarrow-1\le y\le1\)

Vậy \(y_{min}=-1\) khi \(cos3x=0\)

\(y_{max}=1\) khi \(cos3x=1\)