Question 10: A radioactive substance has a half-life of 1620 years. (a) If its mass is now 4 g (grams), how much will be left 810 years from now? (a) Find the time \( t_{1} \) when 1.5 g of the substance remain.

3. \( \frac{1}{y^{-2}}= \)

4. \( 8 \sqrt{2}+4 \sqrt{2}-3 \sqrt{2}= \)

1. A man does a work in 36 days. In how mon many men will plough in int day? 2.25 men plough a field in 30 days. How many

Parker is 6 feet, 2 inches tall. His brother is 4 feet, 9 inches tall. How many inches taller is Parker than his brother?

Soit la suite \( \left(u_{n}\right) \) définie sur \( \mathbb{N} \) par : \[ \left(u_{n}\right):\left\{\begin{array}{l}u_{0}=3 \\ u_{n+1}=-6+u_{n}\end{array}\right. \] Si la suite \( \left(u_{n}\right) \) est géométrique ou arithmétique, donner sa raison \( r \), sinon écrire "aucun":