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3 years ago

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A model rocket fired from the ground at time t can be modeled by the equation h= -490t² + 1120t. When is the height of the model

rocket 640 centimeters?

1 answer:

galben [10]3 years ago

6 0

9514 1404 393

Answer:

t = 1 1/7 ≈ 1.1429 seconds

Step-by-step explanation:

Filling in the given height, we can solve for t:

640 = -490t^2 +1120t

49t^2 -112t +64 = 0 . . . . . divide by 10, put in standard form

(7t -8)^2 = 0

t = 8/7 . . . . . . . the value of t that makes the factor(s) zero

The model rocket will reach its maximum height of 640 cm after 1 1/7 seconds.

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3 years ago

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71 points what is 12x 8=...........................96

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2 years ago

A superhero is trying to leap over a tall building. The function f(x)=-16x^2+200x gives the superhero's height in feet as a func

Gemiola [76]

Answer:

Since $\bigtriangleup \geq 0$ , the superhero makes it over the building.

Step-by-step explanation:

The height is given by the following function:

$f(x) = -16x^{2} + 200x$

Will the superhero make it over the building?

We have to find if there is values of x for which f(x) = 612.

Solving a quadratic equation:

Given a second order polynomial expressed by the following equation:

$ax^{2} + bx + c, a\neq0$ .

This polynomial has roots $x_{1}, x_{2}$ such that $ax^{2} + bx + c = a(x - x_{1})*(x - x_{2})$ , given by the following formulas:

$x_{1} = \frac{-b + \sqrt{\bigtriangleup}}{2*a}$

$x_{2} = \frac{-b - \sqrt{\bigtriangleup}}{2*a}$

$\bigtriangleup = b^{2} - 4ac$

If $\bigtriangleup < 0$ , the polynomial has no solutions.

In this question:

$f(x) = -16x^{2} + 200x$

$-16x^{2} + 200x = 612$

$16x^{2} - 200x + 612 = 0$

We have to find $\bigtriangleup$

We have that $a = 16, b = -200, c = 612$ . So

$\bigtriangleup = (-200)^{2} - 4*16*612 = 832$

Since $\bigtriangleup \geq 0$ , the superhero makes it over the building.

7 0

3 years ago

Part 4: Use the information provided to write the vertex formula of each parabola.

sergey [27]

Answer: 1. x = (y - 2)² + 8

$\bold{2.\quad x=-\dfrac{1}{2}(y-10)^2}+1$

3. y = 2(x +9)² + 7

<u>Step-by-step explanation:</u>

Notes: Vertex form is: y =a(x - h)² + k or x =a(y - k)² + h

(h, k) is the vertex
point of vertex is midpoint of focus and directrix: $\dfrac{focus+directrix}{2}$

$\bullet\quad a=\dfrac{1}{4p}$

p is the distance from the vertex to the focus

1)

$focus = \bigg(\dfrac{-31}{4},2\bigg)\qquad directrix: x=\dfrac{-33}{4}\\\\\text{Since directrix is x, then the x-value of the vertex is:}\\\\\dfrac{focus+directrix}{2}=\dfrac{\frac{-31}{4}+\frac{-33}{4}}{2}=\dfrac{\frac{-64}{4}}{2}=\dfrac{-16}{2}=-8\\\\\text{The y-value of the vertex is given by the focus as: 2}\\\\\text{vertex (h, k)}=(-8,2)$

Now let's find the a-value:

$p=focus-vertex\\\\p=\dfrac{-31}{4}-\dfrac{-32}{4}=\dfrac{1}{4}\\\\\\a=\dfrac{1}{4p}=\dfrac{1}{4(\frac{1}{4})}=\dfrac{1}{1}=1$

Now, plug in a = 1 and (h, k) = (-8, 2) into the equation x =a(y - k)² + h

x = (y - 2)² + 8

***************************************************************************************

2)

$focus = \bigg(\dfrac{1}{2},10\bigg)\qquad directrix: x=\dfrac{3}{2}\\\\\text{Since directrix is x, then the x-value of the vertex is:}\\\\\dfrac{focus+directrix}{2}=\dfrac{\frac{1}{2}+\frac{3}{2}}{2}=\dfrac{\frac{4}{2}}{2}=\dfrac{2}{2}=1\\\\\text{The y-value of the vertex is given by the focus as: 10}\\\\\text{vertex (h, k)}=(1,10)$

Now let's find the a-value:

$p=focus-vertex\\\\p=\dfrac{1}{2}-\dfrac{2}{2}=\dfrac{-1}{2}\\\\\\a=\dfrac{1}{4p}=\dfrac{1}{4(\frac{-1}{2})}=\dfrac{1}{-2}=-\dfrac{1}{2}$

Now, plug in a = -1/2 and (h, k) = (1, 10) into the equation x =a(y - k)² + h

$\bold{x=-\dfrac{1}{2}(y-10)^2}+1$

***************************************************************************************

3)

$focus = \bigg(-9,\dfrac{57}{8}\bigg)\qquad directrix: y=\dfrac{55}{8}\\\\\text{Since directrix is y, then the y-value of the vertex is:}\\\\\dfrac{focus+directrix}{2}=\dfrac{\frac{57}{8}+\frac{55}{8}}{2}=\dfrac{\frac{112}{8}}{2}=\dfrac{14}{2}=7\\\\\text{The x-value of the vertex is given by the focus as: -9}\\\\\text{vertex (h, k)}=(-9,7)$

Now let's find the a-value:

$p=focus-vertex\\\\p=\dfrac{57}{8}-\dfrac{56}{8}=\dfrac{1}{8}\\\\\\a=\dfrac{1}{4p}=\dfrac{1}{4(\frac{1}{8})}=\dfrac{1}{\frac{1}{2}}=2$

Now, plug in a = 2 and (h, k) = (-9, 7) into the equation y =a(x - h)² + k

y = 2(x +9)² + 7

4 0

3 years ago

Find the sum of the first 8 terms in the geometric sequence: 1, 3, 9, 27,

Butoxors [25]

The sum of the first 8 items in the geometric sequence:1, 3, 9, 27, ...etc is 3280.

Step-by-step explanation:

The given is,

sequence: 1,3,9,21,.. etc

Step:1

The given is based on multiplication of 3 to previous number,

( x - previous number, next number = 3 × $x$ )

First term : 1

Second term : 1 × 3 = 3

Third term : 3 × 3 = 9

Fourth term : 9 × 3 =27

Fifth term : 27 × 3 = 81

Sixth term : 81 × 3 = 243

Seventh term : 243 × 3 = 729

Eighth term : 729 × 3 = 2187

Step:2

Sum of first 8 terms $= 1 + 3 + 9 + 27 + 81 + 243 + 729 + 2187$

= 3280

Sum of first 8 terms = 3280

Result:

The sum of the first 8 items in the geometric sequence:1, 3, 9, 27, ...etc is 3280.

7 0

3 years ago