## Thursday, February 14, 2013

### Jalaire's Algebra Scribepost

9.3 Questions from the textbook (7, 10, 13, 16)

7. Evaluate each equation using the given value:
a) y = 5x - 3 when x = 6
This question means that you will multiply 6 by 5 and then subtract 3 to get your answer of 27
y = 5x - 3
y = 5 (6) - 3
y = 5 x 6 - 3
y = 30 - 3
y = 27

b) y = x - 8 when x = 5
This question means that you will always subtract 8 from x because that's how you will know the next term. In this case, x is 5, so 5 subtract 8 is -3
y = x - 8
y = 5 - 8
y = -3

c) y = -5x when x = -2
This question means that you will multiply -5 to whatever number x is. In this case, x is -2, so -5 multiplied -2 is 10. Because, if you know your integers well, if two numbers is negative and you multiply them together it will always equal a positive.
y = -5x
y = -5 (-2)
y = 10

d) y = x when y = 25
This question means that since y = 25 then, x = 25 also because y and x equal each other.
y = x
25 = x

10. Make a table of values for each equation. Graph each ordered pair.
a) y = 2x
y = 2x             y = 2x
y = 2 (1)          y = 2 (3)
y = 2               y = 6

y = 2x
y = 2 (2)
y = 4

b) y = 3x - 1

y = 3 (3) - 1      y = 3 (9) - 1
y = 9 - 1           y = 27 - 1
y = 8                y = 26

y = 3x - 1

y = 3 (6) - 1
y = 18 - 1
y = 17

c) y = -4x + 5

y = -4x + 5         y = -4x + 5
y = -4 (2) + 5      y = -4 (6) + 5
y = -8 + 5           y = -24 + 5
y = -3                 y = -19

y = -4x + 5
y = -4 (4) + 5
y = -16 + 5
y = -11

d) y = 5 - x

y = 5 - x          y = 5 - x
y = 5 - 5          y = 5 - 15
y = 5 + (-5)      y = 5 + (-15)
y = 0               y = -10

y = 5 - x

y = 5 - 10
y = 5 + (-10)
y = -5

13. a) Graph the ordered pairs:

b) Is it reasonable to assume there are points between the ones on your graph if you have no other information?
Yes, I think it is reasonable to assume that there are points between the values because it doesn't say in the question that says you can't. Numbers with decimal can be also be a linear relation also.

16. The graph shows Nigel's monthly earnings.

a) If Nigel doesn't make any sales, what are his monthly earnings?
It would be \$1200 because in the graph it clearly states that if he makes 0 sales, then he would earn \$1200.

b) Nigel has sales of \$4000 in one month. How much does he earn?
He would earn \$1400 that month because in the graph on x axis you would go to four and see where the coordinate would land.

c) Nigel earns \$1500 in a month. What are his sales?
His sales would be \$6000 because even though it doesn't have the point on the graph, you know that it has a linear relation and that linear relations always have to be in a line, so that's why the answer is \$6000.

Here's a link to teach some tips on graphing.
Here's a video if you need more help.