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2 years ago

Use the Pythagorean Theorem to find an approximate value of x

Mathematics

1 answer:

kozerog [31]2 years ago

7 0

Answer:

Step-by-step explanation:

Hypotenuse² =base² + altitude²

(3x + 4)² = (2x + 1)² + (3x)²

{Use (a+b)² = a² + 2ab + b²}

(3x)² + 2*3x+4 + 4² = (2x)² + 2*2x*1 + 1² + 9x²

9x² + 24x + 16 = 4x² + 4x + 1 + 9x²

9x² + 24x + 16 = 13x² + 4x + 1

0 = 13x² + 4x + 1 - 9x² - 24x - 16

13x² - 9x² + 4x - 24x +1 - 16 = 0

4x² - 20x - 15 = 0

a = 4 ; b =-20 ; c = -15

D = b² - 4ac = (-20)² - 4*4*(-15) = 400 + 240 = 640

√D = √640 = 25.30

$x=\dfrac{-b+\sqrt{D}}{2a} \ ; \ x=\dfrac{-b-\sqrt{D}}{2a}\\\\\\x=\dfrac{20+25.30}{2*4} \ ; \ x=\dfrac{20-25.30}{2*4}\\\\\\x=\dfrac{45.30}{8} \ ; \ x =\dfrac{-5.30}{8}\\\\$

x = 5 .66 ; x = -0.66

Ignore x = -0.66 as length of a side cannot be negative

Answer : x = 5.66

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Write an equation for the following situation: 15 less than a number is equal to 12

weeeeeb [17]

Break it down
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"a number" means unknown or placeholder means x
"is equal to" means '='
'12' means 12
-15+x=12
add 15
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2 years ago

Patrick has just finished building a pen for his new dog. The pen is 3 feet wider than it is long. He also built a doghouse to p

zalisa [80]

General Idea:

(i) Assign variable for the unknown that we need to find

(ii) Sketch a diagram to help us visualize the problem

(iii) Write the mathematical equation representing the description given.

(iv) Solve the equation by substitution method. Solving means finding the values of the variables which will make both the equation TRUE

Applying the concept:

Given: x represents the length of the pen and y represents the area of the doghouse

Statement 1: "The pen is 3 feet wider than it is long"

$Length \; of\; the \; pen = x\\ Width \; of\; the\; pen=x+3$

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Statement 2: "He also built a doghouse to put in the pen which has a perimeter that is equal to the area of its base"

$Area \; of\; the\; Dog \; house=y\\ Perimeter \; of\; Dog\; house=y$

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Statement 3: "After putting the doghouse in the pen, he calculates that the dog will have 178 square feet of space to run around inside the pen."

$Area \; of \; the\; Pen - Area \;of \;the\;Dog \;House=\;Space\;inside\;Pen\\ \\ x \cdot (x+3)-y=178\\ Distributing \;x\;in\;the\;left\;side\;of\;the\;equation\\ \\ x^2+3x-y=178\Rightarrow\; 1^{st}\; Equation\\$

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Statement 4: "The perimeter of the pen is 3 times greater than the perimeter of the doghouse."

$Perimeter\; of\; the\; Pen=3\; \cdot \; Perimeter\; of\; the\; Dog\; House\\ \\ 2(x \; + \; x+3)=3 \cdot y\\ Combine\; like\; terms\; inside\; the\; parenthesis\\ \\ 2(2x+3)=3y\\ Distribute\; 2\; in\; the\; left\; side\; of\; the\; equation\\ \\ 4x+6=3y\\ Subtract \; 6\; and \; 3y\; on\; both\; sides\; of\; the\; equation\\ \\ 4x+6-3y-6=3y-3y-6\\ Combine\; like\; terms\\ \\ 4x-3y=-6 \Rightarrow \; \; 2^{nd}\; Equation\\$