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Keith_Richards [23]
3 years ago
15

10 POINTS!! HELP ASAP!! What is the length of AC?

Mathematics
2 answers:
il63 [147K]3 years ago
8 0

Answer:

D.  144

Step-by-step explanation:

Triangle BAC is similar to triangle DEC, so you can set up a ratio:

\frac{84}{156-x} = \frac{7}{x}

Then cross multiply

84x = 7 (156 - x)

84x = 1092 - 7x

Add 7x to both sides.

91x = 1092

Divide both sides by 91.

x = 12

AC = 156 - x

AC = 156 - 12

AC = 144

My name is Ann [436]3 years ago
4 0

Answer:

D

Step-by-step explanation:

Δ CED and Δ CAB are similar thus the ratios of corresponding sides are equal, that is

\frac{CE}{CA} = \frac{ED}{AB} , substitute values

\frac{x}{156-x} = \frac{7}{84} = \frac{1}{12} ( cross- multiply )

12x = 156 - x ( add x to both sides )

13x = 156 ( divide both sides by 13 )

x = 12

Thus

AC = 156 - x = 156 - 12 = 144 → D

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Find d for the arithmetic series with S17=-170 and a1=2
Irina18 [472]
So, we know the sum of the first 17 terms is -170, thus S₁₇ = -170, and we also know the first term is 2, well

\bf \textit{ sum of a finite arithmetic sequence}\\\\
S_n=\cfrac{n(a_1+a_n)}{2}\qquad 
\begin{cases}
n=n^{th}\ term\\
a_1=\textit{first term's value}\\
----------\\
n=17\\
S_{17}=-170\\
a_1=2
\end{cases}
\\\\\\
-170=\cfrac{17(2+a_{17})}{2}\implies \cfrac{-170}{17}=\cfrac{(2+a_{17})}{2}
\\\\\\
-10=\cfrac{(2+a_{17})}{2}\implies -20=2+a_{17}\implies -22=a_{17}

well, since the 17th term is that much, let's check what "d" is then anyway,

\bf n^{th}\textit{ term of an arithmetic sequence}\\\\
a_n=a_1+(n-1)d\qquad 
\begin{cases}
n=n^{th}\ term\\
a_1=\textit{first term's value}\\
d=\textit{common difference}\\
----------\\
n=17\\
a_{17}=-22\\
a_1=2
\end{cases}
\\\\\\
-22=2+(17-1)d\implies -22=2+16d\implies -24=16d
\\\\\\
\cfrac{-24}{16}=d\implies -\cfrac{3}{2}=d
6 0
3 years ago
Please help for brainliest !!
lesantik [10]
This is my answer. How you think about my answer?

7 0
2 years ago
Calculate the middle number between 1-5 and 7.1
prohojiy [21]

Answer:

-4

Step-by-step explanation:

1-5=-4 (7.1+1)-5=3.1

6 0
3 years ago
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a 36 inch board is to be cut into three pieces so that the piece is twice as long as the first piece and the third piece is 3 ti
ICE Princess25 [194]

Answer:

First piece = 6 inches

Second piece = 12 inches

Third piece = 18 inches

Step-by-step explanation:

Length of the first piece = x

Length of the second piece = 2x

Length of the third piece = 3x

Total length is 36 inches:

x + 2x + 3x = 36

6x = 36

x = 6

Therefore, the lengths are:

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Second piece = 12 inches

Third piece = 18 inches

7 0
3 years ago
Solve 3y^{2} - (y + 2) (y - 2)
hram777 [196]

Answer:

3y^2 - (y + 2) (y - 2) = 0

<=> 3y^2 - (y^2 - 4) = 0

<=> 2y^2 + 4 =0

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=> Because y^2 is always equal or larger than 0, there is no real solution.

Hope this helps!

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8 0
3 years ago
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