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Figure 2 shows a sketch of the curve with the equation $y = f(x)$, $x \in \mathbb{R}$ - Edexcel - A-Level Maths Pure - Question 7 - 2010 - Paper 5

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Figure 2 shows a sketch of the curve with the equation $y = f(x)$, $x \in \mathbb{R}$. The curve has a turning point at $A(3, -4)$ and also passes through the point ... show full transcript

Worked Solution & Example Answer:Figure 2 shows a sketch of the curve with the equation $y = f(x)$, $x \in \mathbb{R}$ - Edexcel - A-Level Maths Pure - Question 7 - 2010 - Paper 5

Step 1

(i) $y = |f(x)|$

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Answer

The point A(3,4)A(3, -4) will be transformed to A(3,4)A'(3, 4) because the output of f(x)f(x) is reflected above the x-axis.

Step 2

(ii) $y = 2f(\frac{1}{2}x)$

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Answer

To find the transformed coordinates of point A(3,4)A(3, -4):

  1. First apply the horizontal transformation,
    • The x-coordinate will change as follows: x=3x = 3 becomes 12(3)=1.5\frac{1}{2}(3) = 1.5.
  2. Then, apply the vertical transformation:
    • The y-coordinate will be y=2(4)=8y = 2(-4) = -8.

Thus, the transformed point is A(1.5,8)A'(1.5, -8).

Step 3

Sketch the curve with equation $y = f(|x|)$

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The curve y=f(x)y = f(|x|) takes the left part of the curve and reflects it to the right side. The turning point A(3,4)A(3, -4) remains at (3,4)(-3, -4) on the left since x|x| maps negative x to positive. Both the points where the curve cuts the y-axis at (0,5)(0, 5) and turning points at (3,4)(3, -4) and (3,4)(-3, -4) should be explicitly marked on the sketch.

Step 4

Find $f(x)$

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Since the curve y=f(x)y = f(x) is a translation of y=x2y = x^2, we need to determine the vertex shift:

If f(x)f(x) is translated down to have a turning point of A(3,4)A(3, -4), we can express it as:

f(x)=(x3)24f(x) = (x - 3)^2 - 4

This equation represents a parabola with vertex at (3,4)(3, -4). The function opens upwards.

Step 5

Explain why the function $f$ does not have an inverse

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Answer

The function f(x)=(x3)24f(x) = (x - 3)^2 - 4 is a quadratic function that opens upwards. Since it has a turning point and is not one-to-one (passes the vertical line test), it does not have an inverse function. For a function to have an inverse, it must be bijective (both one-to-one and onto).

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