Given that k k\,k is an integer that is not divisible by 10, use proof by contradiction to show that there exist no integers x x\,x and y y\,y for which 30x+20y=k30x + 20y = k30x+20y=k.
368 exam-style questions on Edexcel A Level Maths Algebraic Methods, covering 1.1 Proof by Contradiction, 1.2 Algebraic Fractions, 1.3 Partial Fractions, 1.4 Repeated Factors, and 1.5 Algebraic Division. Each one has a worked solution and a mark scheme showing where the marks go.