Mark M. answered 10/12/20
Tutor
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Retired math prof. Calc 1, 2 and AP Calculus tutoring experience.
Let y = f(x) = x2 - 6x
Then, Δy = f(x + Δx) - f(x) = f(5.5) - f(5) = -2.75 - (-5) = 2.25
dy = f'(x)dx = f'(5)(0.5) = 4(0.5) = 2