Use proof by contradiction to show that for all x∈Rx \in \mathbb{R}x∈R
x4+100≥20x2x^4 + 100 \ge 20x^2x4+100≥20x2
Show that the following statement is not true.
"The sum of three consecutive even integers is always a multiple of 12."
Practise Edexcel A Level Maths 1.1 Proof by Contradiction with exam-style questions for A Level Maths. 100 questions, matched to the Edexcel A Level Maths (9MA0) specification and written in Paper 1, Paper 2 and Paper 3 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.