20. square-10+10=20x2=400m^2
circle- 3.14x10^2=3.14x100=314
400-314=86
86m^2
21.i don't get 21 sorry
Answer:

Step-by-step explanation:
To write the factored form, multiply a*c from the standard form
. Here it is 4*1 = 4.
Then find factors of 4 that add to b=-4.
4: 1,2,4
-2+-2 = -4
Split the middle term into -2x+-2x and factor by grouping.

For full circle area is π * R² [here R = radius],
for a sector of circle with angle β, area will be = (β/2) * R², β is in radian,
here let β = 22.5° = (π * 22.5/180) = π/8 radian,
now [(π/8)/2] * R² = 9π, [π/16] * R² = 9π
R² = 9 * 16 = 144,
R = √144 = 12 m
Step-by-step explanation:
yes it is . becoz if you kbow the 5 is to 8 means it is an irrational number