2.3: Exercises
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Find the slope and y-intercept of the line with the given data. Using the slope and y-intercept, write the equation of the line in slope-intercept form.
- Answer
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- y=2 x-4
- y=-x+3
- y=-2 x-2
- y=\dfrac{2}{5} x+3
- y=-x+0 or y=-x
- y=\dfrac{2}{3} x+4
Write the equation of the line in slope-intercept form. Identify slope and y-intercept of the line.
- 4x+2y=8
- 9x-3y+15=0
- -5x-10y=20
- 3x-5y=7
- -12x+8y=-60
- 8x-9y=0
- Answer
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- y=-2 x+4
- y=3 x+5
- y=-\dfrac{1}{2} x-2
- y=\dfrac{3}{5} x-\dfrac{7}{5}
- y=\dfrac{3}{2} x-\dfrac{15}{2}
- y=\dfrac{8}{9} x
Find the equation of the line in point-slope form (Eq. 2.1.2) using the indicated point P_1.
- Answer
-
- y-3=\dfrac{1}{3} \cdot(x-5)
- y-1=-\dfrac{3}{2} \cdot(x-4)
- y+2=-\dfrac{1}{2} \cdot(x-3)
- y-1=1 \cdot(x+1)
Graph the line by calculating a table (as in Example 2.1.1). (Solve for y first, if this is necessary.)
- y=2x-4
- y=-x+4
- y=\dfrac 1 2 x +1
- y=3x
- 8x-4y=12
- x+3y+6=0
- Answer
-
- y=2 x-3
- y=-\dfrac{1}{3} x-2
Determine if the given table describes a function. If so, determine its domain and range. Describe which outputs are assigned to which inputs.
- \begin{array}{|c||c|c|c|c|c|} \hline x & -5 & 3 & -1 & 6 & 0 \\ \hline \hline y & 5 & 2 & 8 & 3 & 7 \\ \hline \end{array} \nonumber
- \begin{array}{|c||c|c|c|c|c|} \hline x & 6 & 17 & 4 & -2 & 4 \\ \hline \hline y & 8 & -2 & 0 & 3 & -1 \\ \hline \end{array} \nonumber
- \begin{array}{|c||c|c|c|c|c|c|} \hline x & 19 & 7 & 6 & -2 & 3 & -11 \\ \hline \hline y & 3 & 3 & 3 & 3 & 3 & 3 \\ \hline \end{array} \nonumber
- \begin{array}{|c||c|c|c|c|c|c|} \hline x & 1 & 2 & 3 & 3 & 4 & 5 \\ \hline \hline y & 5.33 & 9 & 13 & 13 & 17 & \sqrt{19} \\ \hline \end{array} \nonumber
- \begin{array}{|c||c|c|c|c|c|c|} \hline x & 0 & 1 & 2 & 2 & 3 & 4 \\ \hline \hline y & 0 & 1 & 2 & 3 & 3 & 4 \\ \hline \end{array} \nonumber
- Answer
-
- this is a function with domain D=\{-5,-1,0,3,6\} and range R = \{2, 3, 5, 7, 8\}, for example: the input x = −5 gives output y = 5, etc.
- not a function since for x = 4 we have both y = 0 and y = −1
- this is a function with D = \{−11, −2, 3, 6, 7, 19\}, R = \{3\}
- this is a function with D=\{1,2,3,4,5\}, R=\{\sqrt{19}, 5.33,9,13,17\}
- this is not a function
We consider children and their (birth) mothers.
- Does the assignment child to their birth mother constitute a function (in the sense of Definition as stated here)?
- Does the assignment mother to their children constitute a function?
- In the case where the assignment is a function, what is the domain?
- In the case where the assignment is a function, what is the range?
- Answer
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- yes
- no
- the domain for the function in (a) is the set of all children
- the range for the function in (a) is the set of all mothers
A bank offers wealthy customers a certain amount of interest, if they keep more than 1 million dollars in their account. The amount is described in the following table:
\begin{array}{|c||c|} \hline \text { dollar amount } x \text { in the account } & \text { interest amount } \\ \hline \hline x \leq \$ 1,000,000 & \$ 0 \\ \hline \$ 1,000,000<x \leq \$ 10,000,000 & 2 \% \text { of } x \\ \hline \$ 10,000,000<x & 1 \% \text { of } x \\ \hline \end{array} \nonumber
- Justify that the assignment cash amount to interest defines a function.
- Find the interest for an amount of:
- \$50,000
- \$5,000,000
- \$1,000,000
- \$30,000,000
- \$10,000,000
- \$2,000,000
- Answer
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- a given cash amount x determines the interest amount y
- i) \$0, ii) \$100,000, iii) \$0, iv) \$300,000, v) \$200,000, vi) \$40,000
Find a formula for a function describing the given inputs and outputs.
- input: the radius of a circle, output: the circumference of the circle
- input: the side length in an equilateral triangle, output: the perimeter of the triangle
- input: one side length of a rectangle, with other side length being 3, output: the perimeter of the rectangle
- input: the side length of a cube, output: the volume of the cube
- Answer
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- C=2 \pi r
- P=3 a
- P=2 a+6
- V=a^{3}