Question

Calculati:
a) -7+(+9)=?
b) 9+(-7)=?
c) -12+(+3)=?
d) +21 +(-17)=?
Si sa-mi spuneti regula calcularii unui numar intreg!!

Answer 1

$\it a)\ -7+(+9) =-7+9=+2=2\\ \\ b)\ 9+(-7)=9-7=2\\ \\ c)\ -12+(+3)=-12+3=-9\\ \\ d)\ +21+(-17)=21-17=4$

Reguli  de  calcul:

+(+a) = +a

-(-a) = +a

+(-a ) =- (+a) = -a