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3 years ago

Subtract (2x3 + 9x − 8) − (4x2 − 15x + 7).

2 answers:

7 0

2x^3 + 9x - 8 - (4x^2 - 15x + 7)....distribute thru the parenthesis
2x^3 + 9x - 8 - 4x^2 + 15x - 7....combine like terms
2x^3 - 4x^2 + 24x - 15 <==

Charra [1.4K]3 years ago

5 0

Distribute invisible -1

-1(4x^2-15x+7)=-4x^2+15x-7

now we have
2x^3+9x-4x^2+15x-7
group like terms

2x^3-4x^2+9x+15x-8-7
add
2x^3-4x^2+24x-15

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Which factorization is equivalent to this expression?

grigory [225]

Answer:

$10(3x+7)$

Step-by-step explanation:

we have the expression:

$30x + 70$

To factor this expression we need to indentify the components that are common in both terms.

At first glance there is nothing in common, but we can notice that 30 and 70 are multiples of 10, that is:

$10*3=30\\10*7=70$

so we can substitute this into the expression:

$10*3x+10*7$

and now that we have the common term (the number 10) we can factorize it, that is, take out the common term and include a parentheses:

$10(3x+7)$

8 0

2 years ago

A metal cylinder can with an open top and closed bottom is to have volume 4 cubic feet. Approximate the dimensions that require

Aleksandr-060686 [28]

Answer:

$r\approx 1.084\ feet$

$h\approx 1.084\ feet$

$\displaystyle A=11.07\ ft^2$

Step-by-step explanation:

<u>Optimizing With Derivatives </u>

The procedure to optimize a function (find its maximum or minimum) consists in :

Produce a function which depends on only one variable
Compute the first derivative and set it equal to 0
Find the values for the variable, called critical points
Compute the second derivative
Evaluate the second derivative in the critical points. If it results positive, the critical point is a minimum, if it's negative, the critical point is a maximum

We know a cylinder has a volume of 4 $ft^3$ . The volume of a cylinder is given by

$\displaystyle V=\pi r^2h$

Equating it to 4

$\displaystyle \pi r^2h=4$

Let's solve for h

$\displaystyle h=\frac{4}{\pi r^2}$

A cylinder with an open-top has only one circle as the shape of the lid and has a lateral area computed as a rectangle of height h and base equal to the length of a circle. Thus, the total area of the material to make the cylinder is

$\displaystyle A=\pi r^2+2\pi rh$

Replacing the formula of h

$\displaystyle A=\pi r^2+2\pi r \left (\frac{4}{\pi r^2}\right )$

Simplifying

$\displaystyle A=\pi r^2+\frac{8}{r}$

We have the function of the area in terms of one variable. Now we compute the first derivative and equal it to zero

$\displaystyle A'=2\pi r-\frac{8}{r^2}=0$

Rearranging

$\displaystyle 2\pi r=\frac{8}{r^2}$

Solving for r

$\displaystyle r^3=\frac{4}{\pi }$

$\displaystyle r=\sqrt[3]{\frac{4}{\pi }}\approx 1.084\ feet$

Computing h

$\displaystyle h=\frac{4}{\pi \ r^2}\approx 1.084\ feet$

We can see the height and the radius are of the same size. We check if the critical point is a maximum or a minimum by computing the second derivative

$\displaystyle A''=2\pi+\frac{16}{r^3}$