Répondre :
(X-1)^2=x^2 -2x +1
99^2= (100-1)^2
=100^2 -2*100*1 +1
=10000 -200 +1
=9801
b) (x-1)(x+1)= x^2 +x -x -1
=x^2 -1
99*101= (100-1)(100+1)
=10000 +100 -100 -1
=10000 -1
=9999
99^2= (100-1)^2
=100^2 -2*100*1 +1
=10000 -200 +1
=9801
b) (x-1)(x+1)= x^2 +x -x -1
=x^2 -1
99*101= (100-1)(100+1)
=10000 +100 -100 -1
=10000 -1
=9999