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3 years ago

Find the value of y.

Mathematics

1 answer:

UNO [17]3 years ago

4 0

Answer:

$y=\sqrt{55}$

which agrees with answer A

Step-by-step explanation:

Notice there are three right angle triangles for which we can apply the Pythagorean theorem:

In the small triangle at the bottom we have the Pythagorean theorem rendering:

(a)

$5^2+y^2=x^2\\x^2=25+y^2$

in the second right angle triangle on top of the previous one, if we call the vertical side on the right side "z", we have:

(b)

$11^2+y^2=z^2\\z^2=121+y^2$

and finally in the large right angle triangle:

(c)

$z^2+x^2=16^2\\z^2=256-x^2$

We can combine equations b and c to obtain:

$121+y^2=256-x^2\\x^2+y^2=256-121=135\\x^2=135-y^2$

and then combine this and (a) to get:

$25+y^2=135-y^2\\2\,y^2=135-25\\2y^2=110\\y^2=55\\y=\sqrt{55}$

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The given function for the height of the firework is a quadratic function

1. Time at which the firework reaches the maximum height is 1 seconds

2. The maximum height of the firework, is 25 yards

3. Time after which the firework will fall to the ground is (1 + √5) seconds

Reason:

The given function that represents the height of the fireworks with time is

presented as follows;

h(t) = -5·t² + 10·t + 20

1. The time at which the firework reaches its maximum height is given by

the maximum point of the given function as follows;

The x-value of the maximum point of a quadratic function is $x = \dfrac{b}{2 \cdot a}$

Where;

a, and b, are the coefficient of x² and x, in the general form of a quadratic function f(x) = a·x² + b·x + c

By comparison, we have;

$t = -\dfrac{10}{2 \times (-5)} = 1$

The time at which the firework reaches the maximum height is t = 1 seconds

2. The maximum height is given by plugging in the value of t, at the maximum point into the given function as follows;

h(1) = -5×1² + 10×1 + 20 = 25

The maximum height of the firework, f(1) = 25 yards

3 The time at which the firework will fall to the ground, is given by the zero of the function as follows;

When the firework falls to the ground, h(t) = 0 = -5·t² + 10·t + 20

Dividing both sides by (-5) gives;

$\dfrac{0}{-5} = \dfrac{ -5 \cdot t^2 + 10 \cdot t + 20}{-5} = t^2 - 2 \cdot t - 4$

t² - 2·t - 4 = 0

By the quadratic formula $x = \dfrac{-b\pm \sqrt{b^{2}-4\cdot a\cdot c}}{2\cdot a}$ , we get;

$t = \dfrac{2\pm \sqrt{(-2)^{2}-4\times 1\times (-4)}}{2\times 1} = \dfrac{2\pm \sqrt{20}}{2\times 1} = \dfrac{2\pm 2 \times \sqrt{5}}{2\times 1} = 1 \pm \sqrt{5}$

Therefore;

The time after which the firework will fall to the ground, t = 1 + √5 seconds

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brainly.com/question/20628403

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3 years ago

A box with no top is to be constructed from a piece of cardboard whose length measures 12 inches more than its width. The box is

MAXImum [283]

Answer:

Width is 12 inches and height is 4 inches.

Step-by-step explanation:

Let the width of the piece of cardboard be = w inches

Then length is = $w+12$ inches

As given, 4 inch squares are cut from each corner;

So, the width is = $w-8$ inches

Length is = $w+12-8=w+4$ inches

When we are folding the cut portion, that gives the height as = 4 inches

The volume is given by : length x width x height

And volume is given as 256 cubic inches

So, $256=(w+4)(w-8)(4)$

=> $256=(w^{2}-4w-32)4$

=> $64=(w^{2}-4w-32)$

=> $w^{2} -4w=96$

or $w^{2} -4w-96=0$

=> $w^{2} -12w+8w-96=0$

=> $w(w-12)+8(w-12)=0$

We get , $(w+8)=0$ ; w = -8(neglect the negative value)

$(w-12)=0$ ; w = 12 inches

And length = $12+12=24$ inches

Hence, dimensions are : L = 24 inches ; w = 12 inches and h = 4 inches

We can check by putting these values in equation : $256=(w+4)(w-8)(4)$

$256=(12+4)(12-8)(4)$

=> $256=(16)(4)(4)$

=> $256=256$

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