For BRAINLY please help fast I have a D in the class haha

Step-by-step explanation:

We have,

[tex]\displaystyle\sf{\,^{n}C_{n-1}+\,^{n}C_{n-2}}[/tex]

[tex]\displaystyle\sf{=\dfrac{n!}{(n-1)!(n-(n-1))!}+\dfrac{n!}{(n-2)!(n-(n-2))!}}[/tex]

[tex]\displaystyle\sf{=\dfrac{n!}{(n-1)!(n-n+1)!}+\dfrac{n!}{(n-2)!(n-n+2)!}}[/tex]

[tex]\displaystyle\sf{=\dfrac{n!}{(n-1)!(1)!}+\dfrac{n!}{(n-2)!(2)!}}[/tex]

[tex]\displaystyle\sf{=\dfrac{n(n-1)!}{(n-1)!(1)!}+\dfrac{n(n-1)(n-2)!}{(n-2)!(2)!}}[/tex]

[tex]\displaystyle\sf{=\dfrac{n}{1}+\dfrac{n(n-1)}{2}}[/tex]

[tex]\displaystyle\sf{=n+\dfrac{n^2-n}{2}}[/tex]

[tex]\displaystyle\sf{=\dfrac{2n+n^2-n}{2}}[/tex]

[tex]\displaystyle\sf{=\dfrac{n^2+n}{2}}[/tex]

[tex]\displaystyle\sf{=\dfrac{n(n+1)}{2}}[/tex]

Using the combination formula, it is found that the value of the expression is given by:

(b) n(n + 1)/2

[tex]C_{n,x}[/tex] is the number of different combinations of x objects from a set of n elements, given by:

[tex]C_{n,x} = \frac{n!}{x!(n-x)!}[/tex]

In this problem:

[tex]C_{n, n-1} = \frac{n!}{(n-1)!(n - n + 1)!} = \frac{n(n-1)!}{(n-1)!} = n[/tex]

[tex]C_{n, n-2} = \frac{n!}{(n-2)!(n - n + 2)!} = \frac{n(n-1)(n-2)!}{(n-2)!2!} = \frac{n(n-1)}{2}[/tex]

Then, adding these values:

[tex]n + \frac{n(n-1)}{2} = \frac{2n + n^2 - n}{2} = \frac{n(n + 1)}{2}[/tex]

Hence option b is correct.

More can be learned about the combination formula at https://brainly.com/question/25821700

9514 1404 393

Answer:

Step-by-step explanation:

Let q represent the number of quarters. Then the number of nickels is 68-q, and the number of cents in the jar is ...

  25q +5(68 -q) = 800

  20q +340 = 800 . . . . simplify

  20q = 460 . . . . . . . . subtract 340

  q = 23 . . . . . . . . . . . divide by 20; this is the number of quarters

  68-q = 45 . . . . . . . find the number of nickels

The jar contains 23 quarters and 45 nickels.

Answer with Step-by-step explanation:

a) 2 3/4 ÷ 3 = 11/12 feet

11/12 + 11/12 = 1 5/6

Or, you could write an algebraic equation:

 2 3/4 ÷ 3 = x.  (3x = 2 3/4)

x = 11/12

The height of the brick proportion of the wall is 1 5/6

b)

You know that 8 x 2 is 16. Well, you already know that the whole total of fractions, multiplied together, would probably be less that 1 and less than 1/2.

So, your rounded answer should be 16. Or 16 1/2

c)  

Area = 8 1/2 x 2 3/4.

Use Distributive Property to solve the area.

(8 x 2) + (3/4 x 1/2) = x

8 x 2 = 16

3/4 x 1/2 = 3/8

16 + 3/8 = 16 3/8

x = 16 3/8

I think my answer is reasonable because I estimated 16, and 1/2. 3/8 is close to 1/2. That's why my answer is reasonable.

-kiniwih426

Answer: 240¢

Step-by-step explanation:

100¢ in a dollar.

$2.40 * 100 = 240

240¢

Answer:

a total of 9 days

Step-by-step explanation:

20% of 45 is 9

answer

=9days

step by step explanation

20% is always over 100,so you are to do 20 over a hundred of 45 days....since 45 can't divide 100 do 20

[tex] \times [/tex]

45 divide by one hundred and the final answer will be 9

Answer:

Step-by-step explanation:

If there is two  - signs you make it a positive

Answer:

Step-by-step explanation:

To add integers having the same sign, keep the same sign and add the absolute value of each number. To add integers with different signs, keep the sign of the number with the largest absolute value and subtract the smallest absolute value from the largest. Subtract an integer by adding its opposite.

Answer:

3744:\p=11756.16 m^2

Step-by-step explanation:

[tex] {12}^{2} \pi(18 + 9) - {4}^{2} \pi \times 9 = 3744\pi \: \: {m}^{2} [/tex]

Answer:

Emilio compra kg De manzanas a euros el kilo cuanto pagara por Las manzanas

Answer:

emilio compra de manzanas a euros el kilo cuanta pagara por las manzanas

y=-3x+9 this should be the answer you are looking for

Answer:

y = -3x + 5

Step-by-step explanation:

y = -3x + b

-1 = -3(2) + b

-1 = -6 + b

5 = b

How long the meeting last = End time - Starting time

                =  10:25 - 9:30

                =  9:85 - 9:30   [I converted 10:25 to make it easier to see the

                                           subtraction. This is posibble because 1hr = 60mins]

                = 55 mins

Answer:

4x + 28

3x - 30

24x + 30

14x - 7y

Step-by-step explanation:

Use M a t h w a y to solve

Answer:

3x^2

Step-by-step explanation:

Factor 3x^4

3 * x * x * x * x

Factor 15x^3

3 * 5 * x * x * x

Factor 21x^2

3 * 7 * x * x

Common factor is

3 * x * x

Simplify:

3x^2

3x to the power of 2

Answer:

X=7

Step-by-step explanation:

These are supplementary angles. So they measure to 180º. 180º-95º=85º. 85º-10= 84º. 84º÷12x= 7.

Answer:

12x+1°+95°=180° (int angles)

12x+96°=180°

12x=180°-96°

=84°

x=84÷12

=7

Answer:16:21

Step-by-step explanation:

Find the slope of the perpendicular line

When two lines are perpendicular, the product of their slopes is -1. This means that the slopes are negative-reciprocals of each other.

            ⇒  if the slope of one of the lines =  - 6

                 then the slope of the perpendicular line (m) = ¹/₆

Determine the equation

We can now use the point-slope form (y - y₁) = m(x - x₁)) to write the equation for this line:

                              ⇒  y - 20 =  ¹/₆ (x - (-12))

                               ∴  y - 20 = ¹/₆ (x + 12)

We can also write the equation in the slope-intercept form (y=mx+c) like the equation in the question by making y the subject of the equation and expanding the bracket to simplify:

                          since   y - 20 = ¹/₆ (x + 12)

                                      y - 20 =  ¹/₆x + 2

                                              y =  ¹/₆x + 22

∴ the slope-intercept equation of the perpendicular line is y =  ¹/₆ x + 22.

To test my answer, I have included a Desmos Graph that I graphed using the information provided in the question and my answer.

Answer:

(-3,4)

Step-by-step explanation:

the point is on -3 on the x-axis and 4 on the y-axis

Answer:(-3,4)

Step-by-step explanation:took the test and got right

Answer:

y = 5x + 5

Step-by-step explanation:

the slope to be parallel y = 5x + 7 must still be 5. To make the line pass through T, the given point, you plug (-2, -5) into the y= mx + b formula. This becomes( -5 )= 5 (-2) + B, and you solve for b. In this equation, b = 5.

Considering that angles A and C are equal, and the sum of the internal angles of a triangle is 180º, we have that:

The measure of angle A is of: 48º.

The measure of angle B is of: 84º.

The measure of angle C is of: 48º.

-----------------------------

[tex]6(x - 3) = 4(x + 1)[/tex]

[tex]6x - 18 = 4x + 4[/tex]

[tex]2x = 22[/tex]

[tex]x = \frac{22}{2}[/tex]

[tex]x = 11[/tex]

[tex]6(11 - 3) = 6(8) = 48[/tex]

The measure of angle A is of: 48º.

The measure of angle C is of: 48º.

The sum of the internal angles of a triangle is of 180º, and this is used to find the measure of angle B.

[tex]mA + mB + mC = 180[/tex]

[tex]2(48) + mB = 180[/tex]

[tex]mB = 84[/tex]

The measure of angle B is of: 84º.

A similar problem is given at https://brainly.com/question/13216436

Answer:

(0,-6)

Step-by-step explanation:here the answer

Answer:

es la a espero que te ayude corona

Answer:

-1 or -0.5

Step-by-step explanation:

f(x) is a common phrase you will see a lot in more advanced math.

Think of it as saying "Function of X". So, when you see f(-1), that means the function of x=-1.

So, when it's asking what value X is in f(-1), remember that that number is the x value.

I say COULD BE -0.5 if it means what y is when x = -1. This is if AND ONLY IF you have a check button to see if -1 is right or the wrong answer. I doubt it is, but I want you to be successful in your work.

I hope this helps :)

Answer:

I think it is 60w2+2640w−11520

Step-by-step explanation:

pls brailiest

Answer:

5/9-2/12=?

9x8=72

5x8=40

12x6=72

2x6=12

40/72 - 12/72 = 28/72

28/4=7

72/4=18

28/72=7/18