Answer:
See Below
Step-by-step explanation:
The surface area of cylinder is given by the formula:

Where
r is radius ( diameter is 4, so radius is 4/2 = 2)
h is height ( h = 9)
Lets find original surface are:

<u>Halving diameter:</u>
diameter would be 4/2 = 2, so radius would be 2/2 = 1
So, SA would be:

<u>Halving height:</u>
Height is 9, halving would make it 9/2 = 4.5
Now, calculating new SA:

Original SA is
,
Halving diameter makes it 
Halving height makes it 
So, halving diameter does not have same effect as halving height.
Answer:
- Hexagon
- Heptagon
Step-by-step explanation:
The first shape has 6 sides. Hence, it is called a hexagon.
The second shape has 7 sides. Hence, it is called a heptagon.
Answer:
The formula for calculating the width of the window is

Step-by-step explanation:
<u><em>The question in English is</em></u>
A rectangular window is l meters wide and h meters high, with a perimeter of 6 meters and an area of 2m². What is the formula for calculating the width of the window?
we know that
The perimeter of the window is equal to

we have

so

simplify
isolate the variable l
----> equation A
The area of the window is equal to

we have

so
----> equation B
substitute equation A in equation B
solve for w

The formula to solve a quadratic equation of the form
is equal to
in this problem we have

so
substitute in the formula
---> formula for calculating the width of the window