EXERCICE 2:

A=x²+10x+25

= x²+2×5×x+5²

A=(x+5)²

B=x²+6x+9

= x²+2×3×x+3²

B=(x+3)²

C= 36+12x+x²

= 6²+2×6×x+x²

C=(6+x)²

D= 4x²+12x+9

= (2x)²+2×3×2x+3²

D=(2x+3)²

E=16x²+40x+25

= (4x)²+2×4x×5+5²

E=(4x+5)²