A and b do not disappear, as such. They mean the same exact thing as x and h. You could have used h and i if you wanted. They're just variables; you can rewrite the solution I provided with any other letters :)it's similar to how you can write f(x)=x+2 or f(t)=t+2. It doesn't matter which letter you use.
Oct 12th, 2015
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