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Differentiate the following from first principles

a f(x)=4x
b f(x)=-3x
c g(x)=x²-4
d f(x)=2x+5​

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Answer:

Explanation:

The first principles method for differentiation involves finding the limit of the difference quotient as h approaches 0. The difference quotient for a function f(x) is given by:

[f(x + h) - f(x)]/h

a) f(x) = 4x

[f(x + h) - f(x)]/h = [4(x + h) - 4x]/h = (4x + 4h - 4x)/h = 4

Therefore, the derivative of f(x) = 4x is 4.

b) f(x) = -3x

[f(x + h) - f(x)]/h = [-3(x + h) - (-3x)]/h = (-3x - 3h + 3x)/h = -3

Therefore, the derivative of f(x) = -3x is -3.

c) g(x) = x^2 - 4

[f(x + h) - f(x)]/h = [(x + h)^2 - 4 - (x^2 - 4)]/h

= [(x^2 + 2hx + h^2) - x^2]/h = 2x + h

Therefore, the derivative of g(x) = x^2 - 4 is 2x.

d) f(x) = 2x + 5

[f(x + h) - f(x)]/h = [2(x + h) + 5 - (2x + 5)]/h

= (2x + 2h + 5 - 2x - 5)/h = 2

Therefore, the derivative of f(x) = 2x + 5 is 2.

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