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scoundrel [369]
3 years ago
6

A number was written on the board. One student increased the number by 23, but another student decreased the number by 1. The fi

rst student’s result was 7 times greater than the result of the second student. What is the number written on the board?
Mathematics
1 answer:
kodGreya [7K]3 years ago
4 0

Answer:

5

Step-by-step explanation:

let the number written on the board be x.

1st student's number= x +23

2nd student's number= x -1

<em>1</em><em>st</em><em> </em><em>student</em><em>'</em><em>s</em><em> </em><em>number</em><em>=</em><em> </em><em>7</em><em>(</em><em>t</em><em>h</em><em>a</em><em>t</em><em> </em><em>o</em><em>f</em><em> </em><em>the</em><em> </em><em>2nd</em><em> </em><em>student</em><em>)</em><em>,</em>

x +23= 7(x -1)

x +23= 7x -7 <em>(</em><em>expand</em><em>)</em>

7x -x= 23 +7 <em>(</em><em>bring</em><em> </em><em>constant</em><em> </em><em>to</em><em> </em><em>1</em><em> </em><em>side</em><em>)</em>

6x= 30 <em>(</em><em>simplify</em><em>)</em>

x= 30 ÷6 (÷6 on both sides)

x= 5

Thus, the number written on the board is 5.

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MAVERICK [17]

Answer:

89

Step-by-step explanation:

Plug 9 into the equation;

m(9)= (9)^2+8

9^2=81\\81+8=89

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2 years ago
Use Gaussian elimination to write each system in triangular form
Feliz [49]

Answer:

To see the steps to the diagonal form see the step-by-step explanation. The solution to the system is x =  -\frac{1}{9}, y= -\frac{1}{9}, z= \frac{4}{9} and w = \frac{7}{9}

Step-by-step explanation:

Gauss elimination method consists in reducing the matrix to a upper triangular one by using three different types of row operations (this is why the method is also called row reduction method). The three elementary row operations are:

  1. Swapping two rows
  2. Multiplying a row by a nonzero number
  3. Adding a multiple of one row to another row

To solve the system using the Gauss elimination method we need to write the augmented matrix of the system. For the given system, this matrix is:

\left[\begin{array}{cccc|c}1 & 1 & 1 & 1 & 1 \\1 & 1 & 0 & -1 & -1 \\-1 & 1 & 1 & 2 & 2 \\1 & 2 & -1 & 1 & 0\end{array}\right]

For this matrix we need to perform the following row operations:

  • R_2 - 1 R_1 \rightarrow R_2 (multiply 1 row by 1 and subtract it from 2 row)
  • R_3 + 1 R_1 \rightarrow R_3 (multiply 1 row by 1 and add it to 3 row)
  • R_4 - 1 R_1 \rightarrow R_4 (multiply 1 row by 1 and subtract it from 4 row)
  • R_2 \leftrightarrow R_3 (interchange the 2 and 3 rows)
  • R_2 / 2 \rightarrow R_2 (divide the 2 row by 2)
  • R_1 - 1 R_2 \rightarrow R_1 (multiply 2 row by 1 and subtract it from 1 row)
  • R_4 - 1 R_2 \rightarrow R_4 (multiply 2 row by 1 and subtract it from 4 row)
  • R_3 \cdot ( -1) \rightarrow R_3 (multiply the 3 row by -1)
  • R_2 - 1 R_3 \rightarrow R_2 (multiply 3 row by 1 and subtract it from 2 row)
  • R_4 + 3 R_3 \rightarrow R_4 (multiply 3 row by 3 and add it to 4 row)
  • R_4 / 4.5 \rightarrow R_4 (divide the 4 row by 4.5)

After this step, the system has an upper triangular form

The triangular matrix looks like:

\left[\begin{array}{cccc|c}1 & 0 & 0 & -0.5 & -0.5  \\0 & 1 & 0 & -0.5 & -0.5\\0 & 0 & 1 & 2 &  2 \\0 & 0 & 0 & 1 &  \frac{7}{9}\end{array}\right]

If you later perform the following operations you can find the solution to the system.

  • R_1 + 0.5 R_4 \rightarrow R_1 (multiply 4 row by 0.5 and add it to 1 row)
  • R_2 + 0.5 R_4 \rightarrow R_2 (multiply 4 row by 0.5 and add it to 2 row)
  • R_3 - 2 R_4 \rightarrow R_3(multiply 4 row by 2 and subtract it from 3 row)

After this operations, the matrix should look like:

\left[\begin{array}{cccc|c}1 & 0 & 0 & 0 & -\frac{1}{9}  \\0 & 1 & 0 & 0 &   -\frac{1}{9}\\0 & 0 & 1 & 0 &  \frac{4}{9} \\0 & 0 & 0 & 1 &  \frac{7}{9}\end{array}\right]

Thus, the solution is:

x =  -\frac{1}{9}, y= -\frac{1}{9}, z= \frac{4}{9} and w = \frac{7}{9}

7 0
3 years ago
What is the cost per year of raising a child from birth to 18 years old, and paying for 4 years of private college?
borishaifa [10]

Answer:

345700

Step-by-step explanation:

79600+145700+120400=345700

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4 years ago
The production manager is going to present this information to the company's board of directors. Which graph should the manager
viktelen [127]

To best emphasize the number of defects. Manager should use graph 3 (refer the image shown):

If we talk about graph 1, it can also be used but usually we put the time line on the horizontal axis, for the convenience and the quantity to be measured on the y-axis. In the graph 1, the time is placed on the vertical axis (x-axis) so it would not be a good pick for the manager.

Same is the case with graph 2 again we have time on the vertical axis. So it is not a good idea to with graph 2.

Graph 3 could be the best to emphasize the number of defects because first of all time is placed on the horizontal axis and the quantity to be shown is on the vertical axis. Secondly, the range of the vertical axis is less so it is easy to observe the data set on the graph quite distinctively. Therefore, graph 3 is the best pick.

Graph 4 is placed correctly in terms of vertical and horizontal axes but the range of vertical axis is quite high due to which the dispersion or the display of the data is quite compressed and it gets hard to visualize.

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4 years ago
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