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Bepaal $f'\left(x\right)$ vanuit eerste beginsels indien dit gegee word dat $f\left(x\right)=4-7x$ - NSC Mathematics - Question 7 - 2019 - Paper 1

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Bepaal $f'\left(x\right)$ vanuit eerste beginsels indien dit gegee word dat $f\left(x\right)=4-7x$. Bepaal $\frac{dy}{dx}$ indien $y=4x^{4}+\sqrt{x}$. Gege... show full transcript

Worked Solution & Example Answer:Bepaal $f'\left(x\right)$ vanuit eerste beginsels indien dit gegee word dat $f\left(x\right)=4-7x$ - NSC Mathematics - Question 7 - 2019 - Paper 1

Step 1

Bepaal $f'\left(x\right)$ vanuit eerste beginsels indien dit gegee word dat $f\left(x\right)=4-7x$

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Answer

Om f(x)f'\left(x\right) te bepaal, begin ons met die definisie van die afgeleide:
f(x)=limh0f(x+h)f(x)hf'\left(x\right) = \lim_{h \to 0} \frac{f\left(x+h\right) - f\left(x\right)}{h}
Hier is f(x+h)=47(x+h)f\left(x+h\right) = 4 - 7\left(x+h\right) en f(x)=47xf\left(x\right) = 4 - 7x.
Substitueer in die limiet:
f(x)=limh0(47(x+h))(47x)hf'\left(x\right) = \lim_{h \to 0} \frac{\left(4 - 7\left(x+h\right)\right) - \left(4 - 7x\right)}{h}
Simpliceer:
=limh07hh=7= \lim_{h \to 0} \frac{-7h}{h} = -7
Dus, f(x)=7f'\left(x\right) = -7.

Step 2

Bepaal $\frac{dy}{dx}$ indien $y=4x^{4}+\sqrt{x}$

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Answer

Om dydx\frac{dy}{dx} te bepaal, gebruik die afgeleide van elke term:
dydx=16x3+12x12\frac{dy}{dx} = 16x^{3} + \frac{1}{2}x^{-\frac{1}{2}}
Hierdie afgeleide is gebasseer op die reëls van afgeleides soos ddxxn=nxn1.\frac{d}{dx}x^{n} = nx^{n-1}.

Step 3

Bepaal: $\frac{dy}{dx}$ en $\frac{dy}{da}$ gegee: $y=ax^{2}+a$

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Answer

7.3.1
dydx=2ax+0=2ax\frac{dy}{dx} = 2ax + 0 = 2ax

7.3.2
dyda=x2+1\frac{dy}{da} = x^{2} + 1

Step 4

Die kurwe met vergelyking $y=\frac{x+12}{x}$ gaan deur die punt $A\left(2;b\right)$.

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Answer

Om die waarde van bb te vind waar x=2x=2:
b=2+122=7b = \frac{2+12}{2} = 7

Die gradient van die kurwe is:
ml=dydx=12x2m_{l} = \frac{dy}{dx} = \frac{-12}{x^{2}}
bij x=2x=2:
ml=1222=31=3m_{l} = \frac{-12}{2^{2}} = -\frac{3}{1} = -3

Die gradient van die loodregte lyn:
mperp=1ml=13m_{perp} = -\frac{1}{m_{l}} = \frac{1}{3}

Die vergelyking van die loodregte lyn kan gegee word as:
y7=13(x2)y - 7 = \frac{1}{3}(x - 2)
Dus sal die uiteindelike vergelyking wees:
y=13x+193y = \frac{1}{3}x + \frac{19}{3}.

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