Salut!
a = 2/(√7+√5) + 3/(√5-√2) = 2(√7-√5)/2 + 3(√5+√2)/3 =√7-√5+√5+√2=√7+√2
b = 4/(√7+√3) + 1/(√3+√2)= 4(√7-√3)/4 + (√3-√2)/1 = √7-√3+√3-√2 = √7-√2
Mg = √[(√7+√2)(√7-√2)]
Mg = √(7-2)
Mg = √5
Succes!
