1. The following problem is from the Algebra of Abû Kâmil (850-930): Find a number such that if 7 is added to it and the sum multiplied by the root

3 times the number,then the result is 10 times the number. \text { In other words, to solve }(x+7) \sqrt{3 x}=10 x . \text { Hint: put } x=\frac{1}{3} y^{2} \text { 2. Prove: } \sqrt{18}-\sqrt{8}=\sqrt{2} \text { . }