Prove that for positive values of a a\,a and bbb
25ab+4ba≥20 \frac{25a}{b} + \frac{4b}{a} \geq 20 b25a+a4b≥20Prove, by counter example, that this is not true for all values of a a\,a and bbb.
257 exam-style questions on Edexcel A Level Maths Algebraic Methods, covering 7.1 Algebraic Fractions, 7.2 Dividing Polynomials, 7.3 The Factor Theorem, 7.4 Mathematical Proof, and 7.5 Methods of Proof. Each one has a worked solution and a mark scheme showing where the marks go.