def resol_syst_inf(A,b):
    x=[]
    n = np.size(b)
    x[0]= (1/A[0][0])*b[0]
    for i in range(0,n):
        s=0
        for j in range(0,i-1):
            s = s + A[i][j]*x[j]
        x[i] = (1/A[i][i])*(b[i]-s)
    print(x)


def resol_syst_sup(A,b):
    x=[]
    n= np.size(b)
    x[n]= (1/A[n][n])*b[n]
    for i in range(0,n-1,-1):
        s=0
        for j in range(i+1,n):
            s = s + A[i][j]*x[j]
        x[i] = (1/A[i][i])*(b[i]-s)
    print(x)