We Added, We Eliminated, We Can Graph
In Chap. 16, we solved the following two-by-two linear system for t and u using double
elimination:
2 t+ 5 u=− 7
and
u= 4 t− 3
We found that t= 4/11 and u=−17/11. Let’s graph this situation, calling t the independent
variable and u the dependent variable.
Find two points for each line
As before, let’s find the u-intercepts and the solution, using these points as the basis for drawing
our lines. The second equation is already in SI form. The u-intercept for its graph is −3, so we
know that (0, −3) is on the line. We have to work on the first equation a little. We start with
2 t+ 5 u=− 7
x
y
(0,990)
(0,–750)
x–y= 750
Each axis
increment
is 200 units
x+y= 990
Solution = (870,120)
Figure 17-2 Graphs of x−y= 750 and x+y= 990
as a two-by-two linear system where
the independent variable is x and the
dependent variable is y. On both axes,
each increment represents 200 units.
We Added, We Eliminated, We Can Graph 267
