A) -9
-7(x+9)=9(x-5)-14x
-7x-63=9x-45-14x
-45 -45
-7x-18=9x-14x
+7x +7x
-18=9x+7x-14x
-18=2x
(-18)/2=(2x)/2
-9=x
7-4=3
10-7=3
13-10=3
we can see that this is an arithmetic sequence with a difference of 3
the nth term=the first term +(n-1) times the difference
so a(n)=4+3(n-1)
True
1/2 (up the hill) - 1/2 (down the hill) = 0
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