1. В выпуклом четырехугольнике \( A B C D A B=C D, \angle B= \) \( =70^{\circ}, \angle B C A=60^{\circ}, \angle A C D=50^{\circ} \). Докажите, что \( B C=A D \). 2. Середина отрезка \( B D \) является центром окружности с диаметром \( A C \), причем точки \( A, B, C, D \) не лежат на од- ной прямой. Докажите, что \( \angle A B C=\angle A D C \).

\( f x+1 / x=5 \), what is \( x^{2}+\frac{1}{x^{2}} ? \)

5) \( a^{3}-3 a^{2}-28 a \)

\begin{tabular}{|l||}\hline \multicolumn{1}{|c||}{ Choosing a Cell Phone Plan } \\ \hline You are choosing between two different cell phone plans. The first plan charges a rate of 21 cents per \\ minute. The second plan charges a monthly fee of \( \$ 39.95 \) plus 8 cents per minute. How many minutes \\ would you have to use in a month in order for the second plan to be preferable? Round your answer to \\ the nearest minute. \\ The second plan will be less expensive if I use minutes or more. \\ \hline\end{tabular}

46 Un'índustria tessile per confezionare delle tovaglie, ognuna con una superficie di \( 210 \mathrm{dm}^{2} \), acquista 31,5 dam \( ^{2} \) di stoffa spendendo € 20000. Calcola quanto guadagna l'azienda se ogni tovaglia viene venduta a \( € 23 \). [ \( € \) 14500]

3) Si \( 2 a-b=5 \) y \( c-2 d=4 \), entonces ¿Cuál es el valor de de la expresión: \( 4 a+2 c-2 b-4 d \) ? A) ? B) C) 18 D' 18