Answer
a) $(1,2), (8,2), (3,4)$
b) Please see the graph, 7 square units
Work Step by Step
a)
$x-y=-1$
$y=2$
$-.4x-y=-5.2$
$x-y=-1$
$y=2$
$x-2=-1$
$x-2+2=-1+2$
$x= 1$
$(1,2)$ is a point
$y=2$
$-.4x-y=-5.2$
$-.4x-2=-5.2$
$-.4x-2+2 = -5.2+2$
$-.4x = -3.2$
$-.4x/-.4 = -3.2/-.4$
$x = 8$
$(8,2)$ is a point
$x-y=-1$
$-.4x-y=-5.2$
$x-y=-1$
$x = y-1$
$-.4x-y=-5.2$
$-.4(y-1)-y=-5.2$
$-.4y+.4-y = -5.2$
$-1.4y+.4=-5.2$
$-1.4y+.4-.4=-5.2-.4$
$-1.4y = -5.6$
$-1.4y/-1.4 = -5.6/-1.4$
$y = 4$
$x-y=-1$
$x-4=-1$
$x-4+4=-1+4$
$x=3$
$(3,4)$ is a point
b)
Distance of base determined from points on line $x=2$. The two points are $(1,2)$ and $(8,2)$. ($8-1=7$, the base)
Height determined from distance $(3,4)$ is from $y=2$, which is 2 ($4-2=2$).
$7*2*1/2 = 7$ square units
