## Shortest Distance Between Two Skew Lines

Evaluate |AB X CD| where A is (6, -3, 0), B is (3, -7, 1), C is (3, 7, -1) and D is (4,5,-3). Hence find the shortest distance between AB and CD The two key points two remember here

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## Proof by Induction

Prove that $$\sum_{r=1}^n rr! = (n+1)!-1$$ for $$n>1$$ In order to prove a mathematical identity, one needs to show that the identity is valid for all the values in the desired range. Trying all the values in

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## Solution Banks for Edexcel Heinemann Textbooks

Visit our new page for the Maths A-level from 2017 solutionbanks I have uploaded solution banks for all the Edexcel Heinemann textbooks. They are in pdf format so can be opened without Internet Explorer.

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