By completing the square, verify that the roots of the equation
x2+px+4=0 x^2 + px + 4 = 0 x2+px+4=0are
x=−p2±p24−4 x = -\frac{p}{2} \pm \sqrt{\frac{p^2}{4} - 4} x=−2p±4p2−4Hence verify that the set of values of p p\,p for which the equation has no real roots is
−4<p<4 -4 < p < 4 −4<p<4322 exam-style questions on Edexcel A Level Maths Quadratics, covering 2.1 Solving Quadratics, 2.2 Completing the Square, 2.3 Sketching Quadratic Graphs, 2.4 The Discriminant, and 2.5 Modelling with Quadratics. Each one has a worked solution and a mark scheme showing where the marks go.