If the system of linear equations  x+y+z=5,   x+2y+2z=6,   x+3y+λz=uhas infinitely many solutions, then the value of λ+u is

Augments matrix =1115122613λμ                                      =R2→R2-R1, R3→R3-R1 1116011102λ-1μ-5                                         =R3→R3-2R1 1115011100λ-3μ-7Given system has infinitely many solutions⇒λ−3=0,    u−7=0⇒λ=3,    u=7⇒λ+ u  =  3+7=10