a=2v3 +3v5+5v7
b=5v7-2v3
a+b=..............
a-b=.............
v=radical !!
Va rog sa-mi explicati cu ati facut.

[tex]a=2 \sqrt{3} +3 \sqrt{5} +5 \sqrt{7} \\ b=5 \sqrt{7} -2 \sqrt{3} \\ a+b=2 \sqrt{3} +3 \sqrt{5} +5 \sqrt{7} +5 \sqrt{7} -2 \sqrt{3} =3 \sqrt{5} +10 \sqrt{7} \\ a-b=2 \sqrt{3} +3 \sqrt{5} +5 \sqrt{7} -(5 \sqrt{7} -2 \sqrt{3} )= \\ =2 \sqrt{3} +3 \sqrt{5} +5 \sqrt{7} -5 \sqrt{7} +2 \sqrt{3} =4 \sqrt{3} +3 \sqrt{5} [/tex]