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Edexcel IGCSE Math A Higher 2.7.HB quadratic formula and completing square

Edexcel IGCSE Math A Higher 2.7.HB quadratic formula and completing square
Edexcel IGCSE Math A syllabusMath A 4MA1First assessment 2018

Practise the formula-comparison question by matching the denominator and discriminant in the solution form to values in the equation.

How this is tested

  • Use the denominator 2a in the quadratic formula to identify the value of a.
  • Compare the discriminant expression with the surd form to find the missing constant.

Question 20

[Maximum number: 3]

Here is a quadratic equation.

ax2+4x+c=0ax^2+4x+c=0

The solutions of this equation are given by

x=−4±23910x=\frac{-4\pm2\sqrt{39}}{10}

Find the value of a and the value of c.
Show your working clearly.

a=c=\begin{gathered} a= \\ c= \end{gathered}