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Sketch the graph of y = 4 - |2x - 6| Solve the inequality Solve the inequality 4 - |2x - 6| > 2 - AQA - A-Level Maths Pure - Question 4 - 2020 - Paper 1

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Sketch the graph of y = 4 - |2x - 6| Solve the inequality Solve the inequality 4 - |2x - 6| > 2

Worked Solution & Example Answer:Sketch the graph of y = 4 - |2x - 6| Solve the inequality Solve the inequality 4 - |2x - 6| > 2 - AQA - A-Level Maths Pure - Question 4 - 2020 - Paper 1

Step 1

Sketch the graph of y = 4 - |2x - 6|

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Answer

To sketch the graph of the function, we need to determine the critical points and the overall shape of the graph. This function will produce an inverted V shape due to the absolute value.

  1. Find the vertex: Set the expression inside the absolute value to zero to find the vertex.

    0=2x60 = 2x - 6

    2x=62x = 6

    x=3x = 3

    We substitute x=3x = 3 into the function:

    y=42(3)6=40=4y = 4 - |2(3) - 6| = 4 - |0| = 4

    Hence, the vertex is at (3, 4).

  2. Find x-intercepts: Set y = 0:

    0=42x60 = 4 - |2x - 6|

    2x6=4|2x - 6| = 4

    This gives two cases:

    • Case 1: 2x6=42x - 6 = 4 leads to 2x=102x = 10 or x=5x = 5.
    • Case 2: 2x6=42x - 6 = -4 leads to 2x=22x = 2 or x=1.x = 1.

    Thus, the x-intercepts are at (1, 0) and (5, 0).

  3. Y-intercept: Set x=0x = 0:

    y=42(0)6=46=46=2.y = 4 - |2(0) - 6| = 4 - | - 6| = 4 - 6 = -2.

    So the y-intercept is at (0, -2).

The graph will have an inverted V shape pointing downwards, intersecting the y-axis at (0, -2), and the x-axis at (1, 0) and (5, 0), with the vertex at (3, 4). Labels for these points should be included on the graph.

Step 2

Solve the inequality

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Answer

To solve the inequality

42x6>24 - |2x - 6| > 2:

  1. Isolate the absolute value:

    42>2x64 - 2 > |2x - 6|

    2>2x62 > |2x - 6|

  2. Set up two inequalities based on the definition of absolute value:

    • Case 1: 2x6<22x - 6 < 2 leads to 2x<82x < 8 or x<4x < 4.

    • Case 2: (2x6)<2-(2x - 6) < 2 leads to 2x6<22x - 6 < 2 or 2x<82x < 8, which simplifies to the same inequality x<4x < 4.

  3. Combine these with the other part derived from the absolute value inequality:

    2x6>22x - 6 > -2 leads to 2x>42x > 4 or x>2x > 2.

  4. Final solution: Therefore, combining both inequalities gives:

    2<x<4.2 < x < 4.

    The solution is the interval (2, 4).

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