SOLUTION: The total question is the following: Graph the inequalities 9x+8y<72 and -7x-4y<=28 to find their solution set. Also, find their point of intersection. I also had to choose a grap

Algebra ->  Graphs -> SOLUTION: The total question is the following: Graph the inequalities 9x+8y<72 and -7x-4y<=28 to find their solution set. Also, find their point of intersection. I also had to choose a grap      Log On


   

Question 871241: The total question is the following:
Graph the inequalities 9x+8y<72 and -7x-4y<=28 to find their solution set. Also, find their point of intersection. I also had to choose a graphing method for 9x+8y<72. I found the slope to be -9/8 with the y intercept being 0, 9. I then had to find a graphing method for -7x-4y<=28. I found that the slope was -7/4 and the y-intercept was 0,-7. I am unable to find the x and y coordinates of the intersection points.
Answer by josgarithmetic(39618) About Me  (Show Source):
You can put this solution on YOUR website!
You can treat the two inequalities as equations and find that point of intersection.

8y=-9x%2B72
y=%28-9x%2B72%29%2F8

-4y=7x%2B28
y=%287x%2B28%29%2F%28-4%29

%28-9x%2B72%29%2F8=%287x%2B28%29%2F%28-4%29
%2872-9x%29%2F8=%287x%2B28%29%2F%28-4%29
mult b.s. by 8
72-9x=-2%287x%2B28%29
72-9x=14x-56
72%2B56=14x%2B9x
23x=
highlight%28x=128%2F23%29, meaning highlight%28y=63%2F23%29

Does that point satisfy the inequality system?
9x+8y<72 AND -7x-4y<=28
9(128/23)+8(63/23)<72 AND -7(128/23)-4(63/23)<=28 ?
IF BOTH TRUE, then you include this intersection point; otherwise exclude this point.