⇔ = 0 → = 5 ⇔ = 0 → = 5 − = ⇔ = 0 → = −1 ⇔ = 0 → = 1 D 4 − 2 = 20 2 + = 6 − = ⇔ = 0 → = −10 ⇔ = 0 → = 5 + = ⇔ = 0 → = 6 ⇔ = 0 → = 3 E 2 + = 6 2 + 4 = 12 + = ⇔ = 0 → = 6 ⇔ = 0 → = 3 + = 69