We need to prove 2*√7 is an irrational number.
Steps:
1) To prove that 2√7 is an irrational, assume the product is rational and set it equal to a/b , where b is not equal to 0.
2) Isolating the radical gives 2= a/√7b.
3) The right side of the equation is irrational.
4) Because the left side of the equation is rational, this is a contradiction.
5) Therefore, the assumption is wrong, and the product is irrational.