Idk what linear combination is but you can solve this way:
3x+y=4
-2x-y=-5
x=-1
3(-1)+y=4
-3+y=4
y=7
So x=-1 and y=7
4/5 of the original amount at the start of the month will remain. The amount at the start of every month will change. Thus:
an = 4/5 (an-1) ; where a1 = 500.
<span>the coordinates of vertex A = (1,1)
</span><span>the coordinates of vertex B = (2,3)
</span><span>the coordinates of vertex C = (2,1)
</span>
D. (5,-21) would be your answer