Using a graph to solve the given system of equations

Question

−3x−3y=6

−x+3y=18

Answer 1

-3x-3y = 6

divide by -3

x+y =-6

y = -x-2

1st equation is a downward sloping line, -45 degrees with the x axis and y intercept = (0,-6), with x intercept = (-2,0)

-x+3y = 18

3y =x+18

y = x/3 +6

2nd equation is an upward sloping line, slope = 1/3, with y intercept = (0,6) and x intercept = (18,0)

they intersect where x/3+6 = -x-2

4x/3 = -8

x = -6 and y = 4, the point (-6,4)

graph the 2 lines, they intersect at (-6,4)

use a graphing calculator, on line or handheld

or carefully graph the two lines by hand on graph paper, preferably or a good sketch