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Figure 2 shows a sketch of the graph with equation y = 2|x + 4| - 5 The vertex of the graph is at the point P, shown in Figure 2 - Edexcel - A-Level Maths Pure - Question 12 - 2020 - Paper 2

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Question 12

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Figure 2 shows a sketch of the graph with equation y = 2|x + 4| - 5 The vertex of the graph is at the point P, shown in Figure 2. (a) Find the coordinates of P. ... show full transcript

Worked Solution & Example Answer:Figure 2 shows a sketch of the graph with equation y = 2|x + 4| - 5 The vertex of the graph is at the point P, shown in Figure 2 - Edexcel - A-Level Maths Pure - Question 12 - 2020 - Paper 2

Step 1

Find the coordinates of P.

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Answer

The vertex form of the equation is given as:

y = 2|x + 4| - 5.

To find the coordinates of the vertex P, we need to determine where the expression inside the absolute value is zero:

Setting the equation inside the absolute value to zero:

x+4=0x + 4 = 0

Solving for x gives: x=4x = -4

Now, substituting this value into the equation to find y:

y = 2|(-4) + 4| - 5 = 2|0| - 5 = -5.

Thus, the coordinates of P are P(-4, -5).

Step 2

Solve the equation 3x + 40 = 2|x + 4| - 5.

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Answer

To solve the equation, we first rewrite it:

3x+40=2x+453x + 40 = 2|x + 4| - 5

This simplifies to:

3x+45=2x+43x + 45 = 2|x + 4|

Now we will consider two cases based on the definition of the absolute value.

Case 1: When x+40x + 4 \geq 0 (i.e., x4x \geq -4):

Then, x+4=x+4|x + 4| = x + 4 and substituting gives us:

3x+45=2(x+4)3x + 45 = 2(x + 4)

Solving for x: 3x+45=2x+83x + 45 = 2x + 8 x=37.x = -37.

This solution is only valid if 374-37 \geq -4, which it is not.

Case 2: When x+4<0x + 4 < 0 (i.e., x<4x < -4):

Then, x+4=(x+4)|x + 4| = -(x + 4) and substituting gives:

3x+45=2(x+4)3x + 45 = -2(x + 4)

3x+45=2x83x + 45 = -2x - 8 5x=535x = -53

Thus, x=10.6.x = -10.6.

Step 3

find the range of possible values of a, writing your answer in set notation.

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Answer

To determine the values of a such that the line y=axy = ax intersects the graph of y=2x+45y = 2|x + 4| - 5 at least once, we need to analyze the intersection.

The intersection occurs if:

ax=2x+45.ax = 2|x + 4| - 5.

This leads to two branches based on the absolute value

  1. For xo4x o -4 (coming from the left):

y approaches 05=5.0 - 5 = -5.

  1. As xx gets larger, the line will yield positive values, while the expression will continue to increase because of the absolute function.

Thus, to have an intersection, a must be: a>2a > 2

In terms of set notation, the answer is: {a:a>2}\{a: a > 2\}.

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