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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 13 - 2020 - Paper 2

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Question 13

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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 ... 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 13 - 2020 - Paper 2

Step 1

Find the coordinates of P.

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Answer

To find the coordinates of point P, we look at the equation of the graph, which is given by

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

The vertex occurs where the expression inside the absolute value is zero. Setting

x+4=0x + 4 = 0,

we find that

x=4x = -4.

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

y=2(4)+45=205=5.y = 2|(-4) + 4| - 5 = 2|0| - 5 = -5.

Thus, the coordinates of P are

P(4,5)P(-4, -5).

Step 2

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

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Answer

To solve the equation

3x+40=2x+45,3x + 40 = 2|x + 4| - 5,

we first simplify the right side:

3x+40=2x+453x + 40 = 2|x + 4| - 5 3x+45=2x+4.3x + 45 = 2|x + 4|.

Next, we can isolate the absolute value:

x+4=3x+452.|x + 4| = \frac{3x + 45}{2}.

We will solve this by considering two cases for the absolute value.

Case 1: x + 4 ≥ 0

In this case,

x+4=3x+452x + 4 = \frac{3x + 45}{2}.

Multiplying through by 2:

2(x+4)=3x+452(x + 4) = 3x + 45 2x+8=3x+452x + 8 = 3x + 45 x=458=37.x = 45 - 8 = 37.

Case 2: x + 4 < 0

Here,

(x+4)=3x+452-(x + 4) = \frac{3x + 45}{2} x4=3x+452.-x - 4 = \frac{3x + 45}{2}.

Multiplying through by 2:

2x8=3x+45-2x - 8 = 3x + 45 845=5x-8 - 45 = 5x x=535.x = -\frac{53}{5}.

Thus, the two solutions are:

x=37 and x=535.x = 37 \text{ and } x = -\frac{53}{5}.

Step 3

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

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Answer

To find the range of possible values of a, we consider when the line

y=axy = ax

intersects the given graph. For intersections to occur, the slope a must ensure that the line can touch or cross the V-shaped graph. Since the vertex is downward at P(-4, -5), the intersection occurs when

a>2 or a<2.a > 2 \text{ or } a < -2.

Thus, the range of values for a in set notation is:

{a:a>2}{a:a<2}.\{ a : a > 2 \} \cup \{ a : a < -2 \}.

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