77.) x= {-5, 6}
78.) x= {-4, 9}
79.) x= {5/3, 2}
80.) x= {1/9, 3}
81.) x= {-6, 18}
82.) x= {-3√3 +4, 3√3 +4}
83.) x= {-7, -3}
84.) x= {-√85 +9 /2, √85 -9 /2}
Answer:
b) 29π mm²
Step-by-step explanation:
Answer:
6
Step-by-step explanation:
Call pentagon p, circle c and triangle t
We have 2c + 2p = 2p + 2t + c
p = 5, t = 3 so
2c + 2(5) = 2(5) + 2(3) + c
2c + 10 = 10 + 6 + c
2c = 6 + c
c = 6
Since AB = CD the trapezoid is isosceles, which means that ∡A = ∡D
Therefore also ∡2 = ∡3 (they are half of the congruent angles)
For the properties of parallel lines (BD and AD) crossed by a transversal (BD) we have ∡3 = ∡CBD.
Now consider triangles AOD and BCD:
∡OAD (2) = ∡ADO (3) = ∡CBD (3) = ∡CDB (4)
T<span>he sum of the angles of a triangle must be 180°, t</span>herefore:
∡AOD = 180 - ∡2 - ∡3
∡BCD = 180 - ∡3 - ∡4
∡AOD = ∡BCD because their measure is the difference of congruent angles.
The total number of keys equals:
12 + 5 + 11 + 2 = 30 keys
The probability to pick a sliver key is:
12/30 = 2/5
The probability to pick a copper key is:
11/30
Hope that helps
