Notam * = inmultire, / = impartire
10 * 10 - 4 * [9 + (ab + ba) / (a + b)]
Din proprietatile inmultirii, ab = ba =>
=> 100 - 4*[9 + 2ab / (a + b)] = 100 - 4 *(9(a+b) + 2 ab) / (a + b) =
= 100 - (36(a + b) + 2ab)/(a+b) = (100(a + b) - 36(a + b) + 2 ab) / (a + b) =
= (64(a + b) + 2ab) / (a+b)
