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The vector a and the vector b are shown on the grid - Edexcel - GCSE Maths - Question 11 - 2018 - Paper 2

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Question 11

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The vector a and the vector b are shown on the grid. (a) On the grid, draw and label vector -2a (b) Work out a + 2b as a column vector.

Worked Solution & Example Answer:The vector a and the vector b are shown on the grid - Edexcel - GCSE Maths - Question 11 - 2018 - Paper 2

Step 1

On the grid, draw and label vector -2a

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Answer

To find vector -2a, first determine the coordinates of vector a from the grid. Let's assume vector a has a tail at point O(0, 0) and head at (4, 4). Thus, vector a can be represented as:

extbfa=(44) extbf{a} = \begin{pmatrix} 4 \\ 4 \end{pmatrix}

For vector -2a:

  1. Multiply vector a by -2: 2a=2(44)=(88)-2\textbf{a} = -2 \begin{pmatrix} 4 \\ 4 \end{pmatrix} = \begin{pmatrix} -8 \\ -8 \end{pmatrix}
  2. Draw the vector starting from the point O with the head at coordinates (-8, -8). Label this vector appropriately on the grid.

Step 2

Work out a + 2b as a column vector.

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Answer

To find a + 2b, we first need to determine the coordinates of vector b. Let's say vector b has a tail at point O(0, 0) and head at (6, 2). Then, vector b can be represented as:

b=(62)\textbf{b} = \begin{pmatrix} 6 \\ 2 \end{pmatrix}

Next, calculate 2b:

  1. Multiply vector b by 2: 2b=2(62)=(124)2\textbf{b} = 2 \begin{pmatrix} 6 \\ 2 \end{pmatrix} = \begin{pmatrix} 12 \\ 4 \end{pmatrix}

Now, we can find a + 2b:

a+2b=(44)+(124)=(4+124+4)=(168)\textbf{a} + 2\textbf{b} = \begin{pmatrix} 4 \\ 4 \end{pmatrix} + \begin{pmatrix} 12 \\ 4 \end{pmatrix} = \begin{pmatrix} 4 + 12 \\ 4 + 4 \end{pmatrix} = \begin{pmatrix} 16 \\ 8 \end{pmatrix}

Thus, the final result for a + 2b as a column vector is:

a+2b=(168)\textbf{a} + 2\textbf{b} = \begin{pmatrix} 16 \\ 8 \end{pmatrix}

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