Bonjour !
Exercice 21 :
a.(4+(-2)*5)*3
=(4-10)*3
=(-6)*3
=-18
b.8*(-2)-5*(-7)+3
=-16+35+3
=22
c.(7-13)/(5-8)+3*(-2)
=-6/-3 + (-6)
=2-6
=-4
Exercice 22 :
A=(-5+2)^2
=(-5+2)(-5+2)
=25-10-10+4
=9
B=(-5)^2+2
=25+2
=27
C=-2*(-2+4)^2
=-2*(-2+4)(-2+4)
=-2*(4-8-8+16)
=-2*4
=8
D=(-5)^2-6^2
=25-36
=-11
E=[10-(8+5)]^2
=(10-13)^2
=(-3)^2
=9
F=90/(-3)^2
=90/9
=10
Voilà :)
