f+dx = 2(x+dx) - 5
= 2 x + 2 dx -5
f(x) = 2 x - 5
((f(x+dx) - f(x)) = 2 dx
divide by dx
= 2
no need to approach 0 with this, the slope of a straight line is constant.
by the way the derivative of 2 x - 5 is 2
Find the limit as it approaches zero. ( f( x + change in x) - f(x) )/ change in x given f(x)=2x-5.
( change in x = triangle x)
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