Find the direction angle of \( v \) for the following vector. \( v=2 i-4 j \) What is the direction angle of \( v \) ? TRound to one decimal place as needed.)

Постройте график функции и укажите для нее область определения и значения \( x \), при которых \( y>0 \). а) \( у=3 \mathrm{x}^{-3} \);

257. Funksiýalaryň grafigini guruñ: \( \begin{array}{ll}\text { a) } y=x^{2}+6 x ; & \text { c) } y=0,5 x^{2}-4 \\ \text { b) } y=-\frac{1}{2} x^{2}+2 ; & \text { d) } y=\frac{1}{2} x^{2}-3 x\end{array} \)

3. A desintegração de certa substância é descrita pela lei \( M(t)=256(4)^{-0,125 t} \), em que 256 g é a massa inicial dessa substância, \( t \) representa o tempo, em horas e \( M(t) \) a massa, em gramas dessa substância no instante \( t \). Quanto tempo leva para que uma amostra seja reduzida a 32g.

Find \( \|\mathbf{v}\| \). \( \begin{array}{l}\mathbf{v}=9 \mathbf{i}-12 \mathbf{j} \\ \|\mathbf{v}\|=\square \text { (Type an exact answer, using radicals as needed. Simplify your answer.) }\end{array} \)

Use the given functions to answer the question. \( \begin{array}{l}f(x)=2^{x} \\ g(x)=x-3 \\ \text { What is the domain of } \frac{f(x)}{g(x)}=\frac{2^{x}}{x-3} \text { ? } \\ \text { A. the set of all real numbers } \\ \text { B. the set of all real numbers greater than } 0 \\ \text { D. the set of all real numbers not equal to } 0 \\ \text { E. the set of all real numbers not equal to } 3\end{array} \) B. thers greater than 3