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3 years ago

Help me plz!!!!! I have no ideia how to do this

Mathematics

1 answer:

BlackZzzverrR [31]3 years ago

4 0

Answer:

Step-by-step explanation:

In algebra, the goal is always to isolate the variable, so its value can be determined.

<h3>Step 1: Subtract 21</h3>

7x² = -21

<h3>Step 2: Divide by 7</h3>

x² = -3

<h3>Step 3: Check</h3>

7(-3) + 21 = 0

0 = 0 ✔

<h3>Step 4: Answer</h3>

x² = -3

I'm always happy to help :)

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3 years ago

The surface area of a cylinder is increasing at a rate of 9 pi square meters per hour. The height of the cylinder is fixed at 3

Alekssandra [29.7K]

Answer:

$9\pi \text{ cubic meters per hour}$

Step-by-step explanation:

Since, the surface area of a cylinder,

$A= 2\pi r^2 + 2\pi rh$ ................(1)

Where,

r = radius,

h = height,

If $A= 36\pi\text{ square meters}, h = 3\text{ meters}$

$36\pi = 2\pi r^2 + 2\pi r(3)$

$18 = r^2 + 3r$

$\implies r^2 + 3r - 18=0$

$r^2 + 6r - 3r - 18 = 0$ ( by middle term splitting )

$r(r+6)-3(r+6)=0$

$(r-3)(r+6)=0$

By zero product property,

r = 3 or r = - 6 ( not possible )

Thus, radius, r = 3 meters,

Now, differentiating equation (1) with respect to t ( time ),

$\frac{dA}{dt}= 4\pi r\frac{dr}{dt} +2\pi(r\frac{dh}{dt} + h\frac{dr}{dt})$

∵ h = constant, ⇒ dh/dt = 0,

$\frac{dA}{dt} = 4\pi r \frac{dr}{dt} +2\pi h \frac{dr}{dt}$

We have, $\frac{dA}{dt}=9\pi\text{ square meters per hour}, r = h = 3\text{ meters}$

$9\pi = 4\pi (3) \frac{dr}{dt}+2\pi (3)\frac{dr}{dt}$

$9\pi = (12\pi + 6\pi )\frac{dr}{dt}$

$9\pi = 18\pi \frac{dr}{dt}$

$\implies \frac{dr}{dt} =\frac{1}{2}\text{ meter per hour}$

Now,

Volume of a cylinder,

$V=\pi r^2 h$

Differentiating w. r. t. t,

$\frac{dV}{dt}=\pi ( r^2 \frac{dh}{dt}+h(2r)\frac{dr}{dt})=\pi ((3)(6) (\frac{1}{2})) = 9\pi \text{ cubic meters per hour}$

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2 years ago

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Answer:

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Step-by-step explanation:

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3 years ago

Use function notation to write a recursive formula to represent the sequence: 3, 6, 9, …

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Answer:

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Step-by-step explanation:

Substitute $n = 1, 2, 3,..$ to get the recursive formula.

OPTION 1: f(n) = f(n - 1) + 3

Substituting n = 1.

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Substituting n = 2.

f(2) = f(2 - 1) + 3 = f(1) + 3 = 3 + 3 = 6.

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f(3) = f(3 - 1) + 3 = f(2) + 3 = 6 + 3 = 9.

The numbers match the given sequence. So, we say the above recursive formula represents the sequence.

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Substituting n = 1

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