Algebra help?

5x - y  ≤  20

We have to test each ordered pair to see if it makes the equation true.

1.   (10, 8)

5(10) - 8  ≤  20

50 - 8  ≤  20

42  ≤  20     →     false

2.   (5, 6)

5(5) - 6  ≤  20

25 - 6  ≤  20

19  ≤  20     →     true

3.   (2, 1)

5(2)  -  1  ≤  20

10  -  1  ≤  20

9  ≤  20       →     true

4.   (6, 4)

5(6) - 4  ≤  20

30 - 4  ≤  20

26  ≤  20     →     false

The ordered pairs that make the equation true are solutions to the inequality.

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slope  =  \(\frac{\text{change in y}}{\text{change in x}}\,=\,\frac{y_2-y_1}{x_2-x_1}\,=\,\frac{4-2}{-1-5}\,=\,\frac{2}{-6}\,=\,-\frac{1}{3}\)

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y  >  9

First, draw a dotted line at  y = 9 ,

then shade all of the values where y is greater than 9 , which is all of the values above y = 9 .... like this.