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lubasha [3.4K]
3 years ago
13

When solving for x, what is x squared plus 15 equals -8x

Mathematics
1 answer:
VLD [36.1K]3 years ago
5 0

Answer:

x = - 5, x = - 3

Step-by-step explanation:

Given

x² + 15 = - 8x ( add 8x to both sides )

x² + 8x + 15 = 0 ← in standard form

Consider the factors of the constant term (+ 15) which sum to give the coefficient of the x- term (+ 8)

The factors are 5 and 3, since

5 × 3 = 15 and 5 + 3= 8, thus

(x + 5)(x + 3) = 0 ← in factored form

Equate each factor to zero and solve for x

x + 5 = 0 ⇒ x = - 5

x + 3 = 0 ⇒ x = - 3

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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
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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

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∵ The width of the rectangle = y feet

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- Area of a rectangle = length × width

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

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

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

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

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Learn more:

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

#LearnwithBrainly

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