Bjr,
[tex]A = (4\sqrt{5}+7)^2\\\rightarrow (a+b)^2=a^2+2ab+b^2\\\\A = (4\sqrt{5})^2 + 2\times 4\sqrt{5}\times7+(7)^2\\A = 16\times 56\sqrt{5} + 49\\A = 80 + 56\sqrt{5} + 49\\A = 129 + 56\sqrt{5}\\\\B= (12 - 8\sqrt{11})^2\\\rightarrow (a-b)^2=a^2-2ab+b^2\\\\B=(12)^2-2\times 12\times 8\sqrt{11} + (8\sqrt{11})^2\\B = 144 - 192\sqrt{11}+64\times11\\B = 144 - 192\sqrt{11} + 704\\B = 848 - 192\sqrt{11}\\\\C=( 2\sqrt{10} + 4\sqrt{3} ) ( 4\sqrt{3} - 2\sqrt{10} )\\\rightarrow (a+b)(a-b)=a^2-b^2\\\\C = (4\sqrt{3}+2\sqrt{10})(4\sqrt{3} - 2\sqrt{10})\\C = (4\sqrt{3})^2-(2\sqrt{10})^2\\C = 16\times3 - 4\times10\\C = 48 - 40\\C = 8[/tex]
Bonne journée.
