8. The time \( (0) \) in seconds it takes a free-falling object to fall is given by the formula, \( t=\sqrt{\frac{h}{16}} \).How high in feet, will an airplane can reach in 15 seconds? \( \begin{array}{llll}\text { a. } 36 \mathrm{ft} & \text { b. } 60 \mathrm{ft} & \text { c. } 3600 \mathrm{ft} & \text { d. } 6000 \mathrm{ft}\end{array} \)

a) \( \begin{aligned} 4 y+20 & =40 \\ 7 z-15 & =55\end{aligned} \)

56. Вычислите значение выраже \( \frac{\sqrt{5}+\sqrt{7}}{\sqrt{5}-\sqrt{7}}+\frac{\sqrt{5}-\sqrt{7}}{\sqrt{5}+\sqrt{7}} \).

6. Factorise each of the following expressions. \( \begin{array}{ll}\text { (a) } 2 x^{2}+3 x+1 & \text { (b) } 2 x^{2}+7 x+5 \\ \text { (c) } 3 y^{2}-5 y+2 & \text { (d) } 3 y^{2}-11 y+10 \\ \text { (e) } 4 m^{2}-4 m+1 & \text { (f) } 4 m^{2}+4 m-3\end{array} \)

\( z = \sqrt[ 5 ] { - i \overline { z } } \)

11. \( y-7=-10 \)