Mark M. answered 04/19/20
Retired math prof. Calc 1, 2 and AP Calculus tutoring experience.
L = 7(4) + 4 = 32, c = 4, f(x) = 7x + 4
Let δ = 0.01/7 = 0.00143
If l x - 4 l < 0.01/7, then l 7x - 28 l = l (7x + 4) - 32 l < 0.01
So, if l x - c l < 0.01/7, then l f(x) - L l < 0.01
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Let δ = 0.005/7 and proceed as above.