Resolver gráficamente: a) \( \left\{\begin{array}{c}x+y=11 \\ 3 x-y=5\end{array} \quad\right. \) b) \( \left\{\begin{array}{c}2 x-y=7 \\ -x+2 y=-5\end{array}\right. \)

5. Factorise each of the following expressions by splitting the middle term. \( \begin{array}{ll}\text { (a) } x^{2}+3 x+2 & \text { (b) } x^{2}+5 x+6 \\ \text { (c) } y^{2}-7 y+10 & \text { (d) } y^{2}-8 y-9 \\ \text { (e) } z^{2}+2 z-3 & \text { (f) } z^{2}+14 z-15\end{array} \)

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

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

10. \( \frac{7 x+65}{5}=6 \)

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