Complete square then solve equation

A question is this type if and only if it requires completing the square and then using that form to solve a quadratic equation.

12 questions · Moderate -0.7

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Edexcel C1 2005 June Q3
6 marks Moderate -0.8
$$x ^ { 2 } - 8 x - 29 \equiv ( x + a ) ^ { 2 } + b ,$$ where \(a\) and \(b\) are constants.
  1. Find the value of \(a\) and the value of \(b\).
  2. Hence, or otherwise, show that the roots of $$x ^ { 2 } - 8 x - 29 = 0$$ are \(c \pm d \sqrt { } 5\), where \(c\) and \(d\) are integers to be found.
OCR C1 Q1
3 marks Moderate -0.5
  1. Solve the equation
$$x ^ { 2 } - 4 x - 8 = 0$$ giving your answers in the form \(a + b \sqrt { 3 }\) where \(a\) and \(b\) are integers.
OCR C1 Q4
6 marks Moderate -0.3
4. (i) By completing the square, find in terms of the constant \(k\) the roots of the equation $$x ^ { 2 } + 2 k x + 4 = 0 .$$ (ii) Hence find the exact roots of the equation $$x ^ { 2 } + 6 x + 4 = 0 .$$
Edexcel C1 Q1
3 marks Moderate -0.8
  1. The \(n\)th term of a sequence is defined by
$$u _ { n } = n ^ { 2 } - 6 n + 11 , \quad n \geq 1 .$$ Given that the \(k\) th term of the sequence is 38 , find the value of \(k\).
Edexcel C1 Q3
6 marks Moderate -0.8
\(x^2 - 8x - 29 = (x + a)^2 + b\), where \(a\) and \(b\) are constants.
  1. Find the value of \(a\) and the value of \(b\). [3]
  2. Hence, or otherwise, show that the roots of $$x^2 - 8x - 29 = 0$$ are \(c \pm d\sqrt{5}\), where \(c\) and \(d\) are integers to be found. [3]
Edexcel C1 Q15
8 marks Moderate -0.3
  1. By completing the square, find in terms of \(k\) the roots of the equation $$x^2 + 2kx - 7 = 0.$$ [4]
  2. Prove that, for all values of \(k\), the roots of \(x^2 + 2kx - 7 = 0\) are real and different. [2]
  3. Given that \(k = \sqrt{2}\), find the exact roots of the equation. [2]
Edexcel C1 Q4
8 marks Moderate -0.8
  1. By completing the square, find in terms of \(k\) the roots of the equation $$x^2 + 2kx - 7 = 0.$$ [4]
  2. Prove that, for all values of \(k\), the roots of \(x^2 + 2kx - 7 = 0\) are real and different. [2]
  3. Given that \(k = \sqrt{2}\), find the exact roots of the equation. [2]
OCR C1 2006 June Q3
7 marks Moderate -0.8
  1. Express \(2x^2 + 12x + 13\) in the form \(a(x + b)^2 + c\). [4]
  2. Solve \(2x^2 + 12x + 13 = 0\), giving your answers in simplified surd form. [3]
Edexcel C1 Q6
8 marks Moderate -0.8
$$\text{f}(x) = 2x^2 - 4x + 1.$$
  1. Find the values of the constants \(a\), \(b\) and \(c\) such that $$\text{f}(x) = a(x + b)^2 + c.$$ [4]
  2. State the equation of the line of symmetry of the curve \(y = \text{f}(x)\). [1]
  3. Solve the equation \(\text{f}(x) = 3\), giving your answers in exact form. [3]
Edexcel C1 Q5
6 marks Moderate -0.3
  1. By completing the square, find in terms of the constant \(k\) the roots of the equation $$x^2 + 2kx + 4 = 0.$$ [4]
  2. Hence find the exact roots of the equation $$x^2 + 6x + 4 = 0.$$ [2]
OCR C1 Q6
8 marks Moderate -0.8
\(f(x) = 2x^2 - 4x + 1\).
  1. Find the values of the constants \(a\), \(b\) and \(c\) such that $$f(x) = a(x + b)^2 + c.$$ [4]
  2. State the equation of the line of symmetry of the curve \(y = f(x)\). [1]
  3. Solve the equation \(f(x) = 3\), giving your answers in exact form. [3]
Pre-U Pre-U 9794/2 2012 June Q1
5 marks Easy -1.3
  1. Solve the equation \(x^2 - 8x + 4 = 0\), giving your answer in the form \(p \pm q\sqrt{3}\), where \(p\) and \(q\) are integers. [2]
  2. Expand and simplify \((6 + 2\sqrt{3})(2 - \sqrt{3})\). [3]