Réponse :
Bonsoir,
a)
y²-22y+121
=y²-(2*11*y)+11²
--> a²-2ab+b²= (a-b)²
= (y-11)²
c)
100-x²
=10²-x²
--> a²-b²= (a-b)(a+b)
=(10-x)(10+x)
b)
49-14x+x²
=x²-(2*7*x)+7²
--> a²-2ab+b²= (a-b)²
=(x-7)²
d)
y²+y+0,25
=y²+(2*0,5*y)=0.5²
--> a²+2ab+b²= (a+b)²
= (y+0,5)²
Bonne soirée.