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6.1 Determine $f'(x)$ using FIRST PRINCIPLES if $f(x) = \frac{7}{2}x + 5$ - NSC Technical Mathematics - Question 6 - 2023 - Paper 1

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6.1-Determine-$f'(x)$-using-FIRST-PRINCIPLES-if-$f(x)-=-\frac{7}{2}x-+-5$-NSC Technical Mathematics-Question 6-2023-Paper 1.png

6.1 Determine $f'(x)$ using FIRST PRINCIPLES if $f(x) = \frac{7}{2}x + 5$. 6.2 Determine: 6.2.1 $f'(x)$ if $f(x) = -8\pi$ 6.2.2 \( \frac{dy}{dx} \) if $y = \frac... show full transcript

Worked Solution & Example Answer:6.1 Determine $f'(x)$ using FIRST PRINCIPLES if $f(x) = \frac{7}{2}x + 5$ - NSC Technical Mathematics - Question 6 - 2023 - Paper 1

Step 1

Determine $f'(x)$ using FIRST PRINCIPLES if $f(x) = \frac{7}{2}x + 5$

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Answer

To find the derivative using first principles, we apply the formula: f(x)=limh0f(x+h)f(x)hf'(x) = \lim_{h \to 0} \frac{f(x+h) - f(x)}{h} Substituting our function: f(x)=limh0(72(x+h)+5)(72x+5)hf'(x) = \lim_{h \to 0} \frac{\left(\frac{7}{2}(x+h) + 5\right) - \left(\frac{7}{2}x + 5\right)}{h} Simplifying: f(x)=limh072hh=72f'(x) = \lim_{h \to 0} \frac{\frac{7}{2}h}{h} = \frac{7}{2}

Step 2

Determine $f'(x)$ if $f(x) = -8\pi$

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Answer

Since f(x)=8πf(x) = -8\pi is a constant function, its derivative is: f(x)=0f'(x) = 0

Step 3

Determine \( \frac{dy}{dx} \) if $y = \frac{x^4 + 9x}{x^2}$

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Answer

We simplify first: y=x2+9xy = x^2 + \frac{9}{x} Now, using the quotient rule: dydx=(2x)(x2)(x4+9x)(2x)(x2)2\frac{dy}{dx} = \frac{(2x)(x^2) - (x^4 + 9x)(2x)}{(x^2)^2} Expanding gives: dydx=2x3(2x5+18x2)x4=2x516x2x4=2x16x2\frac{dy}{dx} = \frac{2x^3 - (2x^5 + 18x^2)}{x^4} = \frac{-2x^5 - 16x^2}{x^4} = -2x - \frac{16}{x^2}

Step 4

Determine $D_1\left[ \left( \sqrt{x + 8} \right) \right]$

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Answer

To find the first derivative: D1(x+8)=12x+8D_1\left(\sqrt{x + 8}\right) = \frac{1}{2\sqrt{x + 8}}

Step 5

Determine $g'(x)$ if $g(x) = 3x^2 + 9x$

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Answer

Using basic differentiation rules, we find: g(x)=6x+9g'(x) = 6x + 9

Step 6

Determine the gradient of the tangent to the curve of $g$ at the point where $x = -3$

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Answer

Substituting x=3x = -3 into g(x)g'(x) gives: g(3)=6(3)+9=18+9=9g'(-3) = 6(-3) + 9 = -18 + 9 = -9

Step 7

Hence, determine the equation of the tangent to the curve of $g$ where $x = -3$

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Answer

The point on the curve is: g(3)=3(3)2+9(3)=2727=0g(-3) = 3(-3)^2 + 9(-3) = 27 - 27 = 0 The point is (3,0)(-3, 0). Using point-slope form: y0=9(x+3)y - 0 = -9(x + 3) Thus, the equation of the tangent is: y=9x27y = -9x - 27

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