Answer:
C
Explanation:
When a number is connected to a variable, (letter) you are multiplying them.
        
             
        
        
        
Scale = 1cm:3km
Therefore area of lake = 81Km
1:3 = x:81
= 27:81
Therefore the area on map is 27cm
Must click thanks and mark brainliest
 
        
                    
             
        
        
        
Answer:
x = 
Step-by-step explanation:
Given
 -
 -  =
 =  ← factor denominator
 ← factor denominator
 -
 -  =
 = 
[ x ≠ 0, x ≠ - 1 as these would make the terms undefined ]
Multiply through by x(x + 1)
4x² - 5(x + 1) = 4
4x² - 5x - 4 = 4 ( subtract 4 from both sides )
4x² - 5x - 9 = 0 ← in standard form
(x + 1)(4x - 9) = 0 ← in factored form
Equate each factor to zero and solve for x
x + 1 = 0 ⇒ x = - 1
4x - 9 = 0 ⇒ 4x = 9 ⇒ x = 
However, x ≠ - 1 for reason given above, then
solution is x = 
 
        
             
        
        
        
The function you seek to minimize is
()=3‾√4(3)2+(13−4)2
f
(
x
)
=
3
4
(
x
3
)
2
+
(
13
−
x
4
)
2
Then
′()=3‾√18−13−8=(3‾√18+18)−138
f
′
(
x
)
=
3
x
18
−
13
−
x
8
=
(
3
18
+
1
8
)
x
−
13
8
Note that ″()>0
f
″
(
x
)
>
0
 so that the critical point at ′()=0
f
′
(
x
)
=
0
 will be a minimum. The critical point is at
=1179+43‾√≈7.345m
x
=
117
9
+
4
3
≈
7.345
m
So that the amount used for the square will be 13−
13
−
x
, or
13−=524+33‾√≈5.655m