Edexcel P1 2021 June — Question 8

Exam BoardEdexcel
ModuleP1 (Pure Mathematics 1)
Year2021
SessionJune
TopicCurve Sketching
TypeCompleting square from standard form

8. The curve \(C _ { 1 }\) has equation $$y = 3 x ^ { 2 } + 6 x + 9$$
  1. Write \(3 x ^ { 2 } + 6 x + 9\) in the form $$a ( x + b ) ^ { 2 } + c$$ where \(a\), \(b\) and \(c\) are constants to be found. The point \(P\) is the minimum point of \(C _ { 1 }\)
  2. Deduce the coordinates of \(P\). A different curve \(C _ { 2 }\) has equation $$y = A x ^ { 3 } + B x ^ { 2 } + C x + D$$ where \(A\), \(B\), \(C\) and \(D\) are constants. Given that \(C _ { 2 }\)
    • passes through \(P\)
    • intersects the \(x\)-axis at \(- 4 , - 2\) and 3
    • find, making your method clear, the values of \(A , B , C\) and \(D\).
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