Question 104909: I am just beginning with graphing and I am trying to graph y=4x-1 and y=3x+15 to find x. I've solved the equation algebraically but am having a hard time and getting a different outcome each time I graph...and none of them cross at x=16!
I would appreciate any help.
Thanks
Answer by edjones(8007)   (Show Source):
You can put this solution on YOUR website! A) y=4x-1
B) y=3x+15
.
Since these graphs are linear we only need 2 points (x,y) for each line. I like to use the x and y intercepts, if fractions don't get involved, because there are less numbers to deal with, so I make less mistakes.
Keep the x and y as small as possible so the points fit on the graph.
.
y=4x-1
x=0, y= -1 (0,-1)
x=1, y= 4-1=3 (1,3)
.
y=3x+15
x= -5 y= -15+15=0 (-5,0)
x= -3 y= -9+15=6 (-3,6)
.
put the points on your graph paper and draw the lines and it should look like this.
The lines do cross do cross when x=16 when y=63 !!! That is the correct answer.
Check:
63=4*16-1 true
63=3*16+15 true
.
Ed
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