Edexcel C1 — Question 2 4 marks

Exam BoardEdexcel
ModuleC1 (Core Mathematics 1)
Marks4
PaperDownload PDF ↗
Mark schemeDownload PDF ↗
TopicSolving quadratics and applications
TypeFinding quadratic constants from algebraic conditions
DifficultyModerate -0.5 This is a straightforward C1 question requiring completion of the square or using the vertex form. Students need to apply the standard result that the minimum occurs at x = -a/2 and substitute to find both constants. It's slightly easier than average as it's a direct application of well-practiced techniques with no problem-solving insight required.
Spec1.02d Quadratic functions: graphs and discriminant conditions1.02e Complete the square: quadratic polynomials and turning points

2. The curve \(C\) has the equation $$y = x ^ { 2 } + a x + b$$ where \(a\) and \(b\) are constants. Given that the minimum point of \(C\) has coordinates \(( - 2,5 )\), find the values of \(a\) and \(b\).

AnswerMarks Guidance
quadratic, coeff of \(x^2 = 1\), minimum \((-2, 5)\) ∴ \(y = (x + 2)^2 + 5 = x^2 + 4x + 9\)M1 A1, M1 A1 \(a = 4, b = 9\) (4 marks)
quadratic, coeff of $x^2 = 1$, minimum $(-2, 5)$ ∴ $y = (x + 2)^2 + 5 = x^2 + 4x + 9$ | M1 A1, M1 A1 | $a = 4, b = 9$ (4 marks)
2. The curve $C$ has the equation

$$y = x ^ { 2 } + a x + b$$

where $a$ and $b$ are constants.

Given that the minimum point of $C$ has coordinates $( - 2,5 )$, find the values of $a$ and $b$.\\

\hfill \mbox{\textit{Edexcel C1  Q2 [4]}}