SOLUTION: Hi, Can someone help me plot this graph it suppose to be a linear equation in two variables 7x+2y=9 4x+5y=6 I sorry, I been out of school for 15 years and I have forgott

Algebra ->  Exponential-and-logarithmic-functions -> SOLUTION: Hi, Can someone help me plot this graph it suppose to be a linear equation in two variables 7x+2y=9 4x+5y=6 I sorry, I been out of school for 15 years and I have forgott      Log On


   

Question 154484: Hi,
Can someone help me plot this graph it suppose to be a linear equation in two variables
7x+2y=9
4x+5y=6
I sorry, I been out of school for 15 years and I have forgotten how to do these graph.
Again, Thank you for taking the time to help me.
Mark
Found 2 solutions by checkley77, Earlsdon:
Answer by checkley77(12844) About Me  (Show Source):
You can put this solution on YOUR website!
First you need to put these equations in the line form [Y=mX+b] where the [m] term=slope & the [b] term=y intercept.
7x+2y=9
2y=-7x+9
y=-7x/2+9/2
y=-3.5x+4.5 (red line)
4x+5y=6
5y=-4x+6
y=-4x/5+6/5 (green line)
+graph%28+300%2C+200%2C+-6%2C+5%2C+-10%2C+10%2C+-3.5x+%2B4.5%2C+-4x%2F5+%2B6%2F5%29+ (graph 300x200 pixels, x from -6 to 5, y from -10 to 10, of TWO functions -3.5x +4.5 and -4x/5 +6/5).

Answer by Earlsdon(6294) About Me  (Show Source):
You can put this solution on YOUR website!
First, it's helpful to get your equations into the "slope-intercept" form. Remember those? y+=+mx%2Bb where m = the slope and b = the y-intercept.
7x%2B2y+=+9 Subtract 7x from both sides of the equation.
7x-7x%2B2y+=+-7x%2B9 Simplify this.
2y+=+-7x%2B9 Now divide both sides by 2 to get the y by itself.
2y%2F2+=+%28-7x%2B9%29%2F2 Simplify this.
y+=+%28-7%2F2%29x%2B9%2F2
For the second equation:
4x%2B5y+=+6 Subtract 4x from both sides.
5y+=+-4x%2B6 Divide both sides by 5.
y+=+%28-4%2F5%29x+%2B+6%2F5
Since these are linear equations, their graphs will be straight lines and you need only two point to draw a straight line. So, for each equation, first substitute x = 0 and solve for y, then substitute y = 0 then solve for x.
First equation:
The first point:
y+=+%28-7%2F2%29x%2B9%2F2 Substitute x = 0 and solve for y.
y+=+%28-7%2F2%29%280%29%2B9%2F2
y+=+9%2F2 This is one point: (0, 9/2)
The second point:
y+=+%28-4%2F5%29x%2B6%2F5 Substitute y = 0 and solve for x.
0+=+%28-4%2F5%29x%2B6%2F5 Add %284%2F5%29x to both sides.
%284%2F5%29x+=+6%2F5 Multiply both sides by the multiplicative inverse of 4%2F5 and this is 5%2F4
x+=+3%2F2 This is the other point: (3/2, 0) I'll leave the two points for other equation for you to find by using the same technique as above, starting with:
y+=+%28-4%2F5%29x%2B6%2F5
The graph will look like like:
graph%28400%2C400%2C-3%2C3%2C-3%2C6%2C%28-7%2F2%29x%2B9%2F2%2C%28-4%2F5%29x%2B6%2F5%29