5. The chessboard has 8x8 squares. Put 1 grain of rice in the first square, two in the second, four in the third, 8 in the next, then 16 and always double the amount in the next. How many grains are there in the last square?
6. How many pieces are there in total on the chessboard of the previous task?
7. The volume of one grain of rice is about 5mm³. If the grains of rice from the previous task are piled on top of a chessboard in a pyramid whose walls have an inclination of 45°, how big a chessboard is needed?
8. If the rice grains from the previous tasks were stored in a spherical container, what would be the radius of the sphere?
9. If the container were a cube, what would be the length of its side?
10. Is the rice good? What about macaroni? By what percentage will they improve if you season them with curry?
11. Solve the equation: (x+3)(x-5)= 0.
12. Solve the equation: x2 - 2x - 15 = 0.
Hint: Subtract the parentheses from the previous task.