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Harrizon [31]
3 years ago
13

ANSWER ASAP

Mathematics
2 answers:
Aliun [14]3 years ago
8 0
7a - a ^2 - (<span>-4 + 3a^2)
= </span>7a - a ^2 + 4 -  3a^2
=  - 4a^2 + 7a + 4

answer
<span>C) -4a^2 + 7a + 4

</span>
vaieri [72.5K]3 years ago
3 0

Answer:

C) -4a^2 + 7a + 4

Step-by-step explanation:


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A fence must be built to enclose a rectangular area of 20,000 ft^2. Fencing material costs $4 per foot for the two sides facing
Marysya12 [62]

The cost of the least expensive fence is $3200

Step-by-step explanation:

The given is:

  • A fence must be built to enclose a rectangular area of 20,000 ft²
  • Fencing material costs $4 per foot for the two sides facing north and south and ​$8 per foot for the other two sides

We need to find the cost of the least expensive fence

Assume that the length of each side opposite to North or South is x feet and the length of each other sides  is y feet

∵ The length of the rectangle = x feet

∵ The width of the rectangle = y feet

∵ The rectangular area is 20,000 ft²

- Area of a rectangle = length × width

∴ x × y = 20,000

- Divide both sides by x to find y in terms of x

∴ y=\frac{20,000}{x}

The fence's length is equal to the perimeter of the rectangular area

∵ Perimeter of the rectangle = 2 length + 2 width

∴ Perimeter of the rectangle = 2x + 2y

∵ Fencing material costs $4 per foot for the two sides facing

   North and South

∴ x costs $4 per foot

∵ The cost of the other two sides is $8 per foot

∴ y costs $8 per feet

The cost of the fence is the sum of the products of 4 , 2x and 8 , 2y

∵ The cost of the fence (C) = 4(2x) + 8(2y)

∴ C = 8x + 16y

- Substitute y by its value above

∴ C=8x+16(\frac{20,000}{x})

∴ C=8x+\frac{320,000}{x}

To find the least expensive differentiate C with respect to x and equate the answer by 0 to find the value of x

∵ \frac{320,000}{x} can be written as 320,000x^{-1}

∴ C=8x+320,000x^{-1}

∵ \frac{dC}{dx}=8(1)x^{1-1}+320,000(-1)x^{-1-1}

∴ \frac{dC}{dx}=8-320,000x^{-2}

- Equate \frac{dC}{dx} by zero

∴ 8-320,000x^{-2}=0

∵ -320,000x^{-2}=-\frac{320,000}{x^{2}}

∴ 8-\frac{320,000}{x^{2}}=0

- Subtract 8 from both sides

∴ -\frac{320,000}{x^{2}}=-8

- Multiply both sides by x²

∴ - 320,000 = - 8x²

- Divide both sides by -8

∴ 40,000 = x²

- Take √  for both sides

∴ 200 = x

Substitute x in the equation of C to find the least cost of fence

∵ C=8(200)+\frac{320,000}{(200)}

∴ C = 1600 + 1600

∴ C = 3200

The cost of the least expensive fence is $3200

Learn more:

You can learn more about the differentiation in brainly.com/question/4279146

#LearnwithBrainly

5 0
2 years ago
10) The temperature recorded at 12 noon was 15°C above zero. If it decreases at the rateof 3°C per hour until midnight, at what
aalyn [17]

Answer:

at 8 pm the temperature will be -9 degrees. and at midnight the temperature will be negitive twenty one(-21) degrees

Step-by-step explanation:

the start time is 12 pm and finish is 12 am and every hour your going to subtract 3 from the given degree so 15-3= 12 , 12-3=9 ect.

6 0
2 years ago
I hit 20 subs! Can you guys help me out more by subbing to 999 splxsh on yt. Thanks!
charle [14.2K]

Answer:

Sure! I'll look you up!

Step-by-step explanation:

6 0
2 years ago
Read 2 more answers
Biologists tagged 139 fish in a lake on January 1, On February 1, they returned and collected a random sample
Bogdan [553]

Answer:

417 fish

Step-by-step explanation:

139/(10/30)=139*3=417

4 0
3 years ago
Given the formula C= 1/2t(c1-c2), solve for t.
kobusy [5.1K]

Answer:

t=\frac{2C}{c1-c2}

Step-by-step explanation:

C=\frac{1}{2}t(c1-c2)\\2(C)=2(\frac{1}{2}t(c1-c2))\\2C=t(c1-c2)\\\frac{2C}{c1-c2}=\frac{t(c1-c2)}{c1-c2}\\t=\frac{2C}{c1-c2}

3 0
3 years ago
Read 2 more answers
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