OCR Further Pure Core 1 (Further Pure Core 1) 2017 Specimen

Question 8
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8
  1. Find the solution to the following simultaneous equations. $$\begin{array} { r r r } x + y + & z = & 3
    2 x + 4 y + 5 z = & 9
    7 x + 11 y + 12 z = & 20 \end{array}$$
  2. Determine the values of \(p\) and \(k\) for which there are an infinity of solutions to the following simultaneous equations. $$\begin{array} { r r r r } x + & y + & z = & 3
    2 x + & 4 y + & 5 z = & 9
    7 x + & 11 y + & p z = & k \end{array}$$
Question 10
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10 The Argand diagram below shows the origin \(O\) and pentagon \(A B C D E\), where \(A , B , C , D\) and \(E\) are the points that represent the complex numbers \(a , b , c , d\) and \(e\), and where \(a\) is a positive real number. You are given that these five complex numbers are the roots of the equation \(z ^ { 5 } - a ^ { 5 } = 0\).
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  1. Justify each of the following statements.
    (a) \(A , B , C , D\) and \(E\) lie on a circle with centre \(O\).
    (b) \(A B C D E\) is a regular pentagon.
    (c) \(b \times \mathrm { e } ^ { \frac { 2 \mathrm { i } \pi } { 5 } } = c\)
    (d) \(b ^ { * } = e\)
    (e) \(a + b + c + d + e = 0\)
  2. The midpoints of sides \(A B , B C , C D , D E\) and \(E A\) represent the complex numbers \(p , q , r , s\) and \(t\). Determine a polynomial equation, with real coefficients, that has roots \(p , q , r , s\) and \(t\).