Answer:
740
Step-by-step explanation:
The n th term of an arithmetic series is
 = a₁ + (n - 1)d
 = a₁ + (n - 1)d
where a₁ is the first term and d the common difference
Given a₃ = 7 and a₇ = (3 × 7) + 2 = 21 + 2 = 23 , then
a₁ + 2d = 7 → (1)
a₁ + 6d = 23 → (2)
Subtract (1) from (2) term by term
4d = 16 ( divide both sides by 4 )
d = 4
Substitute d = 4 into (1)
a₁ + 2(4) = 7
a₁ + 8 = 7 ( subtract 8 from both sides )
a₁ = - 1
The sum to n terms of an arithmetic series is
 =
 =  [ 2a₁ + (n - 1)d ] , thus
 [ 2a₁ + (n - 1)d ] , thus
 =
 =  [ (2 × - 1) + (19 × 4) ]
 [ (2 × - 1) + (19 × 4) ]
      = 10(- 2 + 76) = 10 × 74 = 740
 
        
             
        
        
        
When taking square roots, you can't take square roots of negative roots of negative numbers. So, what will work for the domain of u(x) is what makes u(x) zero or more. We can make an inequality for that.
u(x) ≥ 0.

9x + 27 ≥ 0 by squaring both sides
9x ≥ -27
x ≥ -3
So the domain of the function is when x ≥ -3 is true.
 
        
             
        
        
        
Answer:
Each tray has 5 colours and one of the colour on the tray is purple. Hence 1/5 of the colours on the tray is purple and thus 1/5 of the colours on the 20 trays is purple. The fraction of colours on the trays will not change. If written out logically, 20 purples out of 100 colours in total on the trays will also given the fraction 1/5.
 
        
             
        
        
        
Answer:
20
Step-by-step explanation:
it is the same length as DC just going diagonal.
(i am not good at explaining in case you could not tell)