Gegee:
f(x) = x(x - 3)^2 met f' (1) = f' (3) = 0 en f(1) = 4
8.1 Toon dat f 'n buigpunt by x = 2 het - NSC Mathematics - Question 8 - 2017 - Paper 1
Question 8
Gegee:
f(x) = x(x - 3)^2 met f' (1) = f' (3) = 0 en f(1) = 4
8.1 Toon dat f 'n buigpunt by x = 2 het.
8.2 Skets die grafiek van f en dui die afsnitte met die ass... show full transcript
Worked Solution & Example Answer:Gegee:
f(x) = x(x - 3)^2 met f' (1) = f' (3) = 0 en f(1) = 4
8.1 Toon dat f 'n buigpunt by x = 2 het - NSC Mathematics - Question 8 - 2017 - Paper 1
Step 1
8.1 Toon dat f 'n buigpunt by x = 2 het.
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Answer
To find the inflection point, we need to determine where the second derivative changes sign. First, we compute the first derivative:
f′(x)=3x2−6x+9
Next, we find the second derivative:
f′′(x)=6x−6
Setting the second derivative equal to zero gives:
6x = 6 \\
x = 1$$
We check the sign of the second derivative around this point. For x < 1, say x = 0, we have:
$$f''(0) = 6(0) - 6 = -6 < 0$$
And for x > 1, say x = 2:
$$f''(2) = 6(2) - 6 = 6 > 0$$
Thus, the concavity changes at x = 1, indicating a point of inflection at x = 2.
Step 2
8.2 Skets die grafiek van f en dui die afsnitte met die asse en die draai punte duidelik aan.
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Answer
To sketch the graph of f, we need to identify key points including the x-intercepts and y-intercept. We previously found that:
The x-intercepts occur at x = 0 and x = 3 (from setting f(x) = 0).
The y-intercept is found by evaluating f(0):
f(0)=0(0−3)2=0
The maximum occurs at (1, 4).
Plotting these points will give a rough sketch of the graph, clearly marking the points of intersection with the axes and indicating the points of inflection at x = 1.
Step 3
8.3 Vir watter waardes van x sal y = -f(x) konkav na onder wees?
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Answer
The function y=−f(x) will be concave down where the second derivative of f(x) is positive, as the negative of a function flips the concavity. We previously found f′′(x)=6x−6. Setting this greater than zero:
6x > 6 \\
x > 1$$
Therefore, for $x > 1$, $y = -f(x)$ will be concave down.
Step 4
8.4.1 Bepaal die koördinate van die lokale maksimum van h indien h(x) = f(x - 2) + 3.
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Answer
To find the local maximum of h(x), we first evaluate the transformation. Since h(x)=f(x−2)+3, we shift the graph of f(x) to the right by 2 units and then up by 3 units. The local maximum from f(x), which occurs at (1, 4) in the original function, becomes:
h(3)=f(1)+3=4+3=7
Thus, the local maximum coordinate in h(x) is (3, 7).
Step 5
8.4.2 Claire beweer dat f ' (2) = 1.
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Answer
To verify Claire's assertion, we compute the first derivative at x = 2:
f′(x)=3x2−6x+9
Substituting x = 2 gives:
e 1$$
Thus, we do not agree with Claire; her statement is incorrect. The gradient at x = 2 is 9, not 1.