6.1 Determine $f'(x)$ using FIRST PRINCIPLES if $f(x) = \frac{7}{2}x + 5$ - NSC Technical Mathematics - Question 6 - 2023 - Paper 1
Question 6
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)=limh→0hf(x+h)−f(x)
Substituting our function:
f′(x)=limh→0h(27(x+h)+5)−(27x+5)
Simplifying:
f′(x)=limh→0h27h=27
Step 2
Determine $f'(x)$ if $f(x) = -8\pi$
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Answer
Since f(x)=−8π is a constant function, its derivative is:
f′(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+x9
Now, using the quotient rule:
dxdy=(x2)2(2x)(x2)−(x4+9x)(2x)
Expanding gives:
dxdy=x42x3−(2x5+18x2)=x4−2x5−16x2=−2x−x216
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Answer
To find the first derivative:
D1(x+8)=2x+81
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+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=−3 into g′(x) gives:
g′(−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)=27−27=0
The point is (−3,0). Using point-slope form:
y−0=−9(x+3)
Thus, the equation of the tangent is:
y=−9x−27