document.write( "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 \n" ); document.write( "

Algebra.Com's Answer #413375 by ankor@dixie-net.com(22740) $\"\"$ $\"About$

You can put this solution on YOUR website!
5x + 4y < 20
\n" ); document.write( "we have to put the equation into the slope/intercept form. (y = mx + b)
\n" ); document.write( "subtract 5x from both sides
\n" ); document.write( "4y < -5x + 20
\n" ); document.write( "divide both sides by 4
\n" ); document.write( "y < $\"-5%2F4\"$ x + 5
\n" ); document.write( "or we could write it
\n" ); document.write( "y < -1.25x + 5
\n" ); document.write( "we solve it just like the equal sign is there with one difference on the graph
\n" ); document.write( "Make a table at least two points, a third would check it for linearity
\n" ); document.write( "let x = 4
\n" ); document.write( "y = -1.25(4) + 5
\n" ); document.write( "y = -5 + 5
\n" ); document.write( "y = 0
\n" ); document.write( ":
\n" ); document.write( " x | y
\n" ); document.write( "-------
\n" ); document.write( " 4 | 0
\n" ); document.write( ":
\n" ); document.write( "let x = 0
\n" ); document.write( "y = -1.25(0) + 5
\n" ); document.write( "y = 5
\n" ); document.write( ":
\n" ); document.write( "now the table
\n" ); document.write( " x | y
\n" ); document.write( "-------
\n" ); document.write( " 4 | 0
\n" ); document.write( " 0 | 5
\n" ); document.write( ":
\n" ); document.write( "let x =-4
\n" ); document.write( "y = -1.25(-4) + 5
\n" ); document.write( "y = +5 + 5
\n" ); document.write( "y = 10
\n" ); document.write( ":
\n" ); document.write( " x | y
\n" ); document.write( "------
\n" ); document.write( " 4 | 0
\n" ); document.write( " 0 | 5
\n" ); document.write( "-4 |10
\n" ); document.write( ":
\n" ); document.write( "Plot these three points, should look like this
\n" ); document.write( " $\"+graph%28+300%2C+200%2C+-6%2C+6%2C+-10%2C+14%2C+-1.25x%2B5%29+\"$
\n" ); document.write( "Now because of the \"<\" sign, the solutions are not on the line but BELOW
\n" ); document.write( "the line, on your graph shade the area below the line, for example the pair
\n" ); document.write( "x=1, y= 2 would fall in this area
\n" ); document.write( "Substitute
\n" ); document.write( "these values in the original equation
\n" ); document.write( "5x + 4y < 20
\n" ); document.write( "5(1) + 4(2) < 20
\n" ); document.write( "5 + 8 < 20
\n" ); document.write( "13 < 20, which is true, 13 is less than 20 \n" ); document.write( "

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