8. As shown in the figure, four small circles with radius r are punched out on the graphic steel plate with radius r, and the area of the remaining part when R=7.8cm and r= 1. 1cm is calculated by using the decomposition factor (π takes 3. 14, leaving two significant figures).

9. A farm plans to build a small reservoir and needs a hollow concrete road. Its specifications are inner diameter d = 45cm, outer diameter D = 75cm and length l = 300cm. Using the decomposition coefficient to calculate how many cubic meters of concrete is needed to pour a section of such a pipeline (π≈3. 14, leaving two significant figures), there is really no figure ... sorry 10. It is known that the square area is 9x2+6xy+y2 (x >; 0, y>0), and the algebraic expression 1 1 representing the side length of a square is written by factorization.

12. The circumference of square I is 96 cm longer than that of square II, and their area difference is 960 cm 2. Find the side length of these two squares.

13. When k is taken, 100x2-kxy+49y2 is a complete square formula.

14.2 to the 48th power is divisible by two numbers between 60 and 70. Find these two numbers.

15

Is this it?