[tex](x+5)(x-5)=x^2-5^2=x^2-25 \\ (25-b)(25+b)=25^2-b^2=625-b^2 \\ (2 \sqrt{3} -3 \sqrt{2} )(2 \sqrt{3} +3 \sqrt{2} )=(2 \sqrt{3} )^2-(3 \sqrt{2} )^2=12-18=-6 \\ (- \sqrt{11} +t)( \sqrt{11} +t)=( \sqrt{11} -t)( \sqrt{11} +t)= \sqrt{11} ^2-t^2=11-t^2[/tex]
