text: ## Precalculus (6th Edition)
  
  $\color{blue}{1}$
  RECALL: (1) $(a+b)(a-b) = a^2-b^2$ (2) For $a\gt0$, $(\sqrt{a})^2 = a$ Use rule (1) above by to obtain: $=2^2 - (\sqrt{3})^2 \\=4-(\sqrt3)^2$ Use rule (2) above to obtain: $\\=4-3 \\=\color{blue}{1}$