Which of the following are valid Bezout identities for gcd(21,35)=7\gcd(21, 35) = 7gcd(21,35)=7?
21⋅2+35⋅(−1)=721 \cdot 2 + 35 \cdot (-1) = 721⋅2+35⋅(−1)=7
21⋅(−3)+35⋅2=721 \cdot (-3) + 35 \cdot 2 = 721⋅(−3)+35⋅2=7
21⋅7+35⋅(−4)=721 \cdot 7 + 35 \cdot (-4) = 721⋅7+35⋅(−4)=7
21⋅1+35⋅1=5621 \cdot 1 + 35 \cdot 1 = 5621⋅1+35⋅1=56