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2 years ago

Write an equation for the perpendicular line to the line whose equation is 4y-5x=20 that contains the point (-2,-3)

Mathematics

1 answer:

yuradex [85]2 years ago

7 0

Answer:

4x + 5y = - 23

Step-by-step explanation:

the equation of a line in slope-intercept form is

y = mx + c ( m is the slope and c the y-intercept )

rearrange 4y - 5x = 20 into this form

add 5x to both sides

4y = 5x + 20 ( divide all terms by 4 )

y = $\frac{5}{4}$ x + 5 ← in slope-intercept form

with slope m = $\frac{5}{4}$

given a line with slope m then the slope of a line perpendicular to it is

$m_{perpendicular}$ = - $\frac{1}{m}$ , hence

$m_{perpendicular}$ = - 1 / $\frac{5}{4}$ = - $\frac{4}{5}$

y = - $\frac{4}{5}$ x + c ← is the partial equation

to find c substitute (- 2, - 3) into the partial equation

- 3 = $\frac{8}{5}$ + c ⇒ c = - $\frac{23}{5}$

y = - $\frac{4}{5}$ x - $\frac{23}{5}$ ← in slope-intercept form

multiply all terms by 5

5y = - 4x - 23 ( add 4x to both sides )

4x + 5y = - 23 ← in standard form

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2 years ago

Amira is painting a rectangular banner 2 1/4 yards wide in the cafeteria. The banner will have a blue background. Amira has enou

elena55 [62]

Area of a rectangle:
A = w x h, where w is the width and h is the height.
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Answer:
The height of a banner is 2/3 yard.

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3 years ago

Read 2 more answers

7) PG & E have 12 linemen working Tuesdays in Placer County. They work in groups of 8. How many

BabaBlast [244]

Part A

Since order matters, we use the nPr permutation formula

We use n = 12 and r = 8

$_{n}P_{r} = \frac{n!}{(n-r)!}\\\\_{12}P_{8} = \frac{12!}{(12-8)!}\\\\_{12}P_{8} = \frac{12!}{4!}\\\\_{12}P_{8} = \frac{12*11*10*9*8*7*6*5*4*3*2*1}{4*3*2*1}\\\\_{12}P_{8} = \frac{479,001,600}{24}\\\\_{12}P_{8} = 19,958,400\\\\$

There are a little under 20 million different permutations.

<h3>Answer: 19,958,400</h3>

Side note: your teacher may not want you to type in the commas

============================================================

Part B

In this case, order doesn't matter. We could use the nCr combination formula like so.

$_{n}C_{r} = \frac{n!}{r!(n-r)!}\\\\_{12}C_{8} = \frac{12!}{8!(12-8)!}\\\\_{12}C_{8} = \frac{12!}{4!}\\\\_{12}C_{8} = \frac{12*11*10*9*8!}{8!*4!}\\\\_{12}C_{8} = \frac{12*11*10*9}{4!} \ \text{ ... pair of 8! terms cancel}\\\\_{12}C_{8} = \frac{12*11*10*9}{4*3*2*1}\\\\_{12}C_{8} = \frac{11880}{24}\\\\_{12}C_{8} = 495\\\\$

We have a much smaller number compared to last time because order isn't important. Consider a group of 3 people {A,B,C} and this group is identical to {C,B,A}. This idea applies to groups of any number.

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

Another way we can compute the answer is to use the result from part A.

Recall that:

nCr = (nPr)/(r!)

If we know the permutation value, we simply divide by r! to get the combination value. In this case, we divide by r! = 8! = 8*7*6*5*4*3*2*1 = 40,320

So,

$_{n}C_{r} = \frac{_{n}P_{r}}{r!}\\\\_{12}C_{8} = \frac{_{12}P_{8}}{8!}\\\\_{12}C_{8} = \frac{19,958,400}{40,320}\\\\_{12}C_{8} = 495\\\\$

Not only is this shortcut fairly handy, but it's also interesting to see how the concepts of combinations and permutations connect to one another.

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

<h3>Answer: 495</h3>

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