5) Sem esboçar o gráfico, escreva se a parábola que representa a funçăo tem concavidad voltada para cima ou para baixo: a) \( y=x^{2}-2 x-7 \) b) \( y=8 x^{2}+4 x-3 \) c) \( y=-4 x^{2} \)

The half-life of radium is 1690 years. If 40 grams are present now, how much will be present in 860 years? \( \square \) grams (Do not round until the final answer. Then round to the nearest thousandth as needed.)

Simplify \( \frac{8}{\sqrt{6}+2} \)

determine whether the given quadratic function has a maximum or a minimum value and then find the value. \( y=-x^{2}+6 x-5 \) \( \begin{array}{lll}\text { [A] minimum, } 3 & \text { [B] minimum, } 4 & \text { [C] maximum, } 4\end{array} \quad \) [D] maximum, 3 A \( \begin{array}{ll}\text { B }\end{array} \) \( \begin{array}{l}\text { C }\end{array} \)

Sarah and Eva took a road trip. Sarah drove two-fifths of the miles. If she drove 128 miles, how many total miles did they drive?

11. Вычислите: \( \frac{10^{7}}{5^{6} \cdot 2^{7}} \)