Question 664458: my daughter has a question 5x+4y<20 she is having a hard time understanding it and how to graph it ,can you help her,please
Answer by ankor@dixie-net.com(22740)   (Show Source):
You can put this solution on YOUR website! 5x + 4y < 20
we have to put the equation into the slope/intercept form. (y = mx + b)
subtract 5x from both sides
4y < -5x + 20
divide both sides by 4
y <  x + 5
or we could write it
y < -1.25x + 5
we solve it just like the equal sign is there with one difference on the graph
Make a table at least two points, a third would check it for linearity
let x = 4
y = -1.25(4) + 5
y = -5 + 5
y = 0
:
x | y
-------
4 | 0
:
let x = 0
y = -1.25(0) + 5
y = 5
:
now the table
x | y
-------
4 | 0
0 | 5
:
let x =-4
y = -1.25(-4) + 5
y = +5 + 5
y = 10
:
x | y
------
4 | 0
0 | 5
-4 |10
:
Plot these three points, should look like this
Now because of the "<" sign, the solutions are not on the line but BELOW
the line, on your graph shade the area below the line, for example the pair
x=1, y= 2 would fall in this area
Substitute
these values in the original equation
5x + 4y < 20
5(1) + 4(2) < 20
5 + 8 < 20
13 < 20, which is true, 13 is less than 20
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