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Elina [12.6K]
3 years ago
15

Which are the solutions of x2 = -7x – 8?

Mathematics
1 answer:
Lady bird [3.3K]3 years ago
6 0

Answer:

( - 7 + √17 ) / 2, ( - 7 - √17 ) / 2

Step-by-step explanation:

x^2 = - 7x - 8

x^2 + 7x + 8 = 0

Here,

a = 1

b = 7

c = 8

D = b^2 - 4ac

= 7^2 - 4 ( 1 ) ( 8 )

= 49 - 32

D = 17

x = - b ± √D / 2a

= - 7 ± √17 / 2 ( 1 )

x = ( - 7 + √17 ) / 2, ( - 7 - √17 ) / 2

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alexgriva [62]

the first solution is 20% acid, and say we'll be using "x" liters, so how many liters of just acid are in it?  well 20% of "x" or namely 0.2x.  Likewise for the 60% acid solution, if we had "y" liters of it, the amount of only acid in it is 0.6y.

\begin{array}{lcccl} &\stackrel{solution}{quantity}&\stackrel{\textit{\% of }}{amount}&\stackrel{\textit{liters of }}{amount}\\ \cline{2-4}&\\ \textit{1st solution}&x&0.20&0.2x\\ \textit{2nd solution}&y&0.60&0.6y\\ \cline{2-4}&\\ mixture&100&0.44&44 \end{array}~\hfill \begin{cases} x+y=100\\\\ 0.2x+0.6y=44 \end{cases}

x+y=100\implies y=100-x~\hfill \stackrel{\textit{substituting on the 2nd equation}}{0.2x+0.6(100-x)=44} \\\\\\ 0.2x+60-0.6x=44\implies -0.4x+60=44\implies -0.4x=-16 \\\\\\ x=\cfrac{-16}{-0.4}\implies \boxed{x=40}~\hfill \boxed{\stackrel{100-40}{y=60}}

7 0
2 years ago
432,2=26<br>275,3=66<br>342,5=41<br>123,4=20<br>then <br>543,2=?​
Readme [11.4K]

Answer:

I think 543,2=24.

hope it helps

5 0
3 years ago
Please answer this question :)
sveticcg [70]

Answer:

a)  49.41

b) not quite sure

Step-by-step explanation:

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6 0
3 years ago
Melinda wants to have a picture window in the shape of a regular hexagon in her new home. She wants the perimeter of the hexagon
salantis [7]
6*x<=9
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7 0
3 years ago
​Ramona's Garage charges the following labor rates. All customers are charged for at least 0.5 hr.
algol13

Answer:

a. The linear function is given by,

y = 60x + 30  [y is in $ and x is in hour and x ≥ 0.5]

  = 60 [for x < 0.5]

b. The total cost of the repair job is,  $ 675 .

Step-by-step explanation:

Let, the linear function describing garage charge( y in $) and no. of hours of repair job ( x in hour) be,

y = mx + c    [for x ≥ 0.5]  -----------(1)

where, m is the slope of the line and c is the y intercept.

Now ,

m = \frac {90 - 60}{1 - 0.5}

  = 60  ----------------(2)

Now, putting the value of m and the point (x,y) = (0.5, 60) in (1), we get,

60 = 60 \times 0.5 + c $

⇒ c = 30 ----------------- (3)  

Hence, the linear function is given by,

y = 60x + 30  [y is in $ and x is in hour and x ≥ 0.5] ------------(4)

  = 60 [for x < 0.5]

Now, putting

x = 4 hr 15 min

= 4\dfrac {15}{60} hour

= 4.25 hour in (4), we get,

y = 60 \times 4.25 + 30  [in $]

= $ 285

So, the total cost of the repair job,

= $ (285 + 390)

= $ 675

3 0
3 years ago
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