3. Decide whether the description matches an optical telescope or radio telescop (a) It picks up radio signals. (b) We look through this telescope. (c) They are best used in a group (an array) (d) It usually can be recognized by its bowl shape. (e) South Africa's biggest is called SALT.

लीटर-मिलीलीटर के जोड़ व घटा के छूवारती प्रश्न रकी टंकी में 25 लीटर तेल था। उसमें से 18 लीटा 375 मिली तेल खर्च हो गय उसमें कितना तेल शेप बचा?

19. Dacă \( \log _{4} 10=m \) să se calculeze \( \log _{8} 250 \). 20. Să se exprime în funcție de \( a=\log _{2} 5 \) numărul: a) \( \log _{8} 80 \); \( \sqrt{2} \) 21. Să se arate că: \( \sqrt{6}+\lg \frac{1}{2}+\lg \frac{2}{3}+\ldots+\lg \frac{999}{1000}=-3 ; \quad \) b) \( \log _{5} \frac{2}{1}+\log _{5} \frac{3}{2}+\log _{5} \frac{4}{3}+ \).

Try \( x_{0}=-2 \) for the following differential equation \( y^{\prime \prime}-x y=0 \).

4) If \( a+b=a b=5 \), then \( a^{2} b+a b^{2}=\ldots \) \( (30,25,15,10) \)

Convert the angle measure to degres, minutes, seconds form. \( \begin{array}{ll}\text { a) } 25.8^{\circ} & \text { b) }-85.36^{\circ}\end{array} \)