Question

Determinar m de modo que se tenha cos x = 4m + 5. *
urgente!!!

Answer 1

$\large\boxed{\begin{array}{l}\sf cos(x)\exists\Longleftrightarrow -1\leqslant cos(x)\leqslant1\\\sf -1\leqslant4m+5\leqslant1\\\sf-1-5\leqslant4m\leqslant1-5\\\sf -6\leqslant4m\leqslant-4\\\sf-\dfrac{6\div2}{4\div2}\leqslant m\leqslant-\dfrac{4}{4}\\\sf-\dfrac{3}{2}\leqslant m\leqslant-1\end{array}}$